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It has been proposed that time, space, and numbers share the same metrics and cortical network, the right parietal cortex. Several recent investigations have demonstrated that the mental number line representation is distorted in neglect patients. The aim of this study is to investigate the relationship between time and spatial configuration in neglect patients. Fourteen right-brain damaged patients (six with neglect and eight without neglect), as well as eight age-matched healthy controls, performed a time discrimination task. A standard tone (short: 700 ms and long: 1,700 ms) had to be confronted in duration to a test tone. Test tone differed of 100, 200, and 300 ms respect to the standard tone duration. Neglect patients performed significantly worse than patients without neglect and healthy controls, irrespective of the duration of the standard tone. These results support the hypothesis that mental representations of space and time both share, to some extent, a common cortical network. Besides, spatial neglect seems to distort the time representation, inducing an overestimation of time durations.
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Time Perception in Spatial Neglect: A Distorted Representation?
Marco Calabria
IRCCS Centro San Giovanni di Dio Fatebenefratelli
Sophie Jacquin-Courtois
INSERM UMR-S 864 “Espace et Action”, Universite´ Claude
Bernard Lyon I, and Institut Fe´de´ratif de Neurosciences de Lyon
Antonio Miozzo
University of Brescia
Yves Rossetti
INSERM UMR-S 864 “Espace et Action”, Universite´ Claude
Bernard Lyon I, and Institut Fe´de´ratif de Neurosciences de Lyon
Alessandro Padovani
University of Brescia
Maria Cotelli
IRCCS Centro San Giovanni di Dio Fatebenefratelli
Carlo Miniussi
IRCCS Centro San Giovanni di Dio Fatebenefratelli and University of Brescia
Objective: It has been proposed that time, space, and numbers share the same metrics and cortical
network, the right parietal cortex. Several recent investigations have demonstrated that the mental
number line representation is distorted in neglect patients. The aim of this study is to investigate the
relationship between time and spatial configuration in neglect patients. Method: Fourteen right-brain
damaged patients (six with neglect and eight without neglect), as well as eight age-matched healthy
controls, performed a time discrimination task. A standard tone (short: 700 ms and long: 1,700 ms) had
to be confronted in duration to a test tone. Test tone differed of 100, 200, and 300 ms respect to the
standard tone duration. Results: Neglect patients performed significantly worse than patients without
neglect and healthy controls, irrespective of the duration of the standard tone. Conclusion: These results
support the hypothesis that mental representations of space and time both share, to some extent, a
common cortical network. Besides, spatial neglect seems to distort the time representation, inducing an
overestimation of time durations.
Keywords: time perception, spatial neglect, brain damaged patients, theory of magnitude, parietal cortex
Converging evidence for similarities in the processing of space,
numbers, and time has recently led to the Theory of Magnitude
(ATOM) (Walsh, 2003). This theory suggests that these three
domains share similar mechanisms, including a common metric for
action, the same accumulator principles and the same neural basis,
the inferior parietal cortex. The relation between numbers and
space is well established and has been demonstrated both in
healthy volunteers and in brain damaged patients (for a review see
Hubbard et al., 2005). In general, healthy participants tend to have
a spatially oriented number representation. This “mental number
line” is typically organized such that small digits are represented
toward the left side of the imagined space, while large digits are
represented toward the right side. Previous findings strongly sug-
gest that number magnitude is represented with a spatial orienta-
tion that develops progressively from left to right.
To date, less attention has been dedicated to the link between
spatial processing and time perception. In behavioral studies, sub-
jects who observe downscaled environments (i.e., a miniature
version) undergo systematic shifts in their experience of time (De
Long, 1981; Mitchell & Davis, 1987). Specifically, they experi-
ence a compression in temporal estimation that is proportional to
the scale-model environments being observed.
Recently, researchers have proposed a spatial-temporal associ-
ation of response codes (STEARC), as a ‘mental time line,’ or a
systematic relation between spatial and time codes for action
(Ishihara, Keller, Rossetti, & Prinz, 2008). In this work, Ishihara
and colleagues (2008) asked participants to estimate the onset time
of the last click of a given sequence. In the congruent condition,
left-sided responses indicated ‘early,’ whereas right-sided response
indicated “later” appearance of the probe. In the noncongruent
condition, the stimulus-response contingency was reversed. The
authors identified a facilitatory effect for compatible responses
(“left”–“early,” “right”–“late”) compared to noncompatible re-
sponses (left–late, right– early), which suggests a space-time rep-
resentation relationship that has the potential to influence percep-
tion and action. The STEARC is an analogous of the SNARC
effect (spatial-numerical association of response codes), such as in
the parity judgment task, participants are quicker to respond to
smaller numbers (e.g., 1 and 2) with the left hand and to larger
numbers (e.g., 8 and 9) with the right hand.
Marco Calabria, IRCCS Centro San Giovanni di Dio Fatebenefratelli;
Sophie Jacquin-Courtois and Yves Rossetti, INSERM UMR-S 864
“Espace et Action”, Universite´ Claude Bernard Lyon I, and Hospices
Civils de Lyon, Institut Fe´de´ratif de Neurosciences de Lyon, Mouvement
et Handicap; Antonio Miozzo and Alessandro Padovani, Clinical Neurology
Department, University of Brescia; Maria Cotelli, IRCCS Centro San Gio-
vanni di Dio Fatebenefratelli; Carlo Miniussi, IRCCS Centro San Giovanni di
Dio Fatebenefratelli and Department of Biomedical Sciences and Biotechnol-
ogies, National Institute of Neuroscience, University of Brescia.
Correspondence concerning this article should be addressed to Marco
Calabria, IRCCS Centro San Giovanni di Dio Fatebenefratelli, Via
PILASTRONI, 4; 25125 Brescia, Italy. E-mail:
Neuropsychology © 2011 American Psychological Association
2011, Vol. 25, No. 2, 193–200 0894-4105/11/$12.00 DOI: 10.1037/a0021304
Vicario, Caltagirone, and Oliveri (2007) showed that optoki-
netic stimulation can influence time estimation. Subjects were
required to make time comparison of time intervals before and
after optokinetic stimulation (leftward or rightward). They found a
directional bias in time perception with only rightward stimulation
inducing an overestimation of time perception compared with
baseline and leftward optokinetic stimulation, suggesting a mental
linear representation of time intervals.
Also neuropsychological research on hemispatial neglect has
considered this issue. Hemispatial neglect is a syndrome charac-
terized by a deficit in interpreting and processing stimuli presented
to the left hemispace, which follows damage to the right hemi-
sphere, and in particular to the inferior parietal lobule (Husain &
Nachev, 2006). Studies with neglect patients have demonstrated
impaired temporal dynamics of spatial attention (Becchio & Ber-
tone, 2006), but few studies to date have investigated time discrim-
ination or interval-production tasks. Basso and colleagues (1996)
tested a patient with hemispatial neglect on short-duration estimation
tasks (300 vs. 700 ms). The patient overestimated durations of stimuli
presented in the leftward space of the right space and underestimated
durations of stimuli presented in the non-neglected field. More re-
cently, Danckert et al. (2007) investigated the ability of neglect
patients to estimate time intervals of seconds.
They found that, compared to healthy controls (HCs), neglect
patients grossly underestimated all durations for intervals greater
than one second. Right-hemisphere damaged patients without ne-
glect also tended to underestimate durations, but their responses
were less inaccurate than those of patients with neglect.
Recently, Cappelletti, Freeman, and Cipolotti (2009) described
a patient, with a right hemisphere lesion. This patient showed
important deficit of time estimation (underestimation), but not of
number and space processing. Nevertheless, an interaction in his
behavior between numbers and time representations as well as
between numbers and space representations was present. Once
again, these results suggest that space, numbers, and time partially
overlap even if they could be impaired selectively.
More recently, some evidence for the spatial representation of
time has been presented in studies that use prism adaptation
(Frassinetti, Magnani, & Oliveri, 2009). Prism adaptation is a
technique to rehabilitate spatial deficits in neglect patients (e.g.,
Luaute, Halligan, Rode, Jacquin-Courtois, & Boisson, 2006). Ne-
glect patients are initially biased to the right, but after sensorimotor
adaptation to the rightward prismatic displacement of the visual
field, this symptom can improve markedly (Rossetti et al., 1998).
Frassinetti et al. (2009) used this technique to shift time perception
in healthy participants. They found that, after prism adaptation,
participants reported an underestimation (if exposed to leftward
deviation) or overestimation (if exposed to rightward deviation) of
time durations, suggesting that time perception may be modified
after sensorimotor adaptation.
The aim of the present study is to investigate the possible
relationship between time and space processing in neglect patients.
We used a time discrimination task, involving a comparison of
duration between a standard auditory stimulus and a test tone. Two
groups of right brain-damaged patients were tested, one with
hemispatial neglect, and the other without hemispatial neglect. In
addition, we tested a group of healthy controls. We compared the
responses to two different durations of standard stimulus (700
or 1,700 ms). Because it has been reported that suprasecond
durations are processed by cortical structures (Mauk & Buono-
mano, 2004), we expected that, for durations longer than one
second, a larger bias would be present in neglect patients, similar
to what happens for spatial elaboration. In particular, if the time
representation follows the same rules as the spatial one it is expected
that the magnitude of the over- or underestimation bias of is linearly
related to the length of the stimulus. As in line bisection has been
shown the longer the line to bisect, the greater the magnitude of the
neglected space (e.g., Halligan & Marshall, 1988).
Moreover, to test the presence of specific lateralization effects in
time discrimination, the presentation of auditory stimuli was lat-
eralized. Standard and test tones were randomly presented con-
tralaterally (e.g., standard at right ear and test at left ear, or vice
versa). At this regard, we expected that time discrimination in the
left space would be more severely impaired than in the right space,
for neglect patients as compared to non-neglect patients and HCs.
Apparatus and Stimuli
Tones were delivered at a suprathreshold level using earphones.
The first stimulus, termed the ‘standard,’ was presented to one ear,
and the second stimulus, termed the ‘test,’ was presented to the
other ear. Presentation order was counterbalanced between the two
sides. Each trial comprised a series of two stimuli, a standard and
a test tone. Standard tones could be of two durations: “short” or
“long” (700 vs. 1,700 ms, respectively). Test tones were presented
at multiple offsets from the standard tones, using differences of
100, 200, or 300 ms. In other words, given a standard of 700 ms,
the test tone could be any of 400, 500, 600, 800, 900, or 1000 ms.
The interstimulus interval was 500 ms and the intertrial interval
was 800 ms. The experiment comprised four blocks of 48 trials
each, for a total of 192 trials, of which 96 featured short and 96
featured long tones.
Participants were required to decide whether the test tone was
shorter or longer than the standard tone. Responses were recorded
via a response-box. Participants used the right hand to respond, or
in the case of motor deficits, the experimenter recorded the re-
sponses (for five patients with neglect). Accuracy was stressed as
being of greatest importance, and there were no response time
restrictions. Stimuli were created using the Test Tone Generator
and presented with Presentation software package, version 11.0
( This software was used both to deliver
tones and to record subjects’ responses.
Eight right-brain damaged patients without hemispatial neglect
(N) (mean age 70.0 10.9 years; mean educa-
tion 6.9 2.4 years) and six right-brain damaged patients who
exhibited hemispatial neglect (N) (mean age 60.3 11.1
year; mean education 9.3 2.6 years) took part in our exper-
iment. Patients were recruited at the Neurological Unit of the
University of Brescia, Italy, and at the Service de Re´e´ducation
Neurologique, Hoˆ pital Henry Gabrielle, Hospices Civils de Lyon,
France. Eight age-matched healthy controls (HC) were also tested
(mean age 67.2 4.5 years; mean education 93.2 years).
Clinical details are listed in Tables 1 and 2. All participants were
right-handed. All gave informed consent and the experimental
protocol was approved by the Ethics Committee of IRCCS San
Giovanni di Dio Fatebenefratelli, Brescia, Italy.
All right-brain damaged patients were assessed for visuospatial abili-
ties (Lezak et al., 2004). The neuropsychological battery included:
A. Line bisection tasks. Line bisection of three different
lengths (5, 10, and 25 cm) presented on A4 format paper and
the Schenkenberg test were performed. The cut-off score for
line bisection was calculated on the basis of an age-matched
Table 1
Clinical and Demographic Characteristic of Patient Groups
Patients Gender
(years) Aethiology
Time from lesion
(days) Lesion site
Patients with spatial
neglect (N)
RB M 65 8 ISCHAEMIC 477 Fronto-parietal
CP M 60 5 ISCHAEMIC 35 Territory of middle cerebral
artery and basal ganglia
RF M 80 13 ISCHAEMIC 150 Temporo-occipital
DO F 49 10 HAEMORRAGIC LOBECTOMY 328 Temporal and partial
LMI M 53 10 ISCHAEMIC 210 Fronto-temporo-parietal
VR F 55 10 ISCHAEMIC 113 Fronto-parietal
Patients without spatial
neglect (N)
MB F 88 8 ISCHAEMIC 15 Frontal and basal ganglia
PG M 72 5 ISCHAEMIC 19 Periventricular white matter
PM F 68 11 HAEMORRAGIC 28 Capsulo-thalamic and basal
ZP F 76 5 ISCHAEMIC 27 Anterior foreharm of
internal capsule
GS M 49 8 ISCHAEMIC 350 Frontal
TM M 67 8 ISCHAEMIC 16 Frontal
CF M 73 5 ISCHAEMIC 172 Superior intraparietal lobule
MA M 67 5 ISCHAEMIC 180 Fronto-temporale
Table 2
Neuropsychological Assessment and PSE of Patient Groups
Neuropsychological assessment
Albert test
PSE right side
Patients with spatial
neglect (N)
RB ⫹⫹26 17 (4) 2 37 55
CP ⫹⫺13 28 (4) 3 31 24
RF ⫹⫹42 31 (8) 3 35 15
DO ⫹⫹13 35 (2) 6 29 74
LMI ⫹⫹28 26 (2) 3 37 89
VR ⫹⫺14 18 (5) 4 18 171
Patients without spatial
neglect (N)
MB ⫺⫺13 0 1
PG ⫺⫺25 0 0 44
PM ⫺⫺32 0 1 20
ZP ⫺⫺35 0 1 30
GS ⫺⫺ 24 0 0 11
TM ⫺⫺ 23 0 0 28
CF ⫺⫺31 0 1 24
MA ⫺⫺13 0 1 19
Cuf-off 60% double tones detected.
Cuf-off 7 mm deviation (“” indicates rightward bias, “” indicates leftward bias).
Cuf-off 15 mm
deviation (“” indicates rightward bias, “” indicates leftward bias); in parentheses the number of omissions.
Cuf-off 2 omissions on the left side
of the sheet.
PSE: point of subjective equivalence; difference between PSE and standard tone duration is reported.
sample of 10 subjects (2 SDs below the mean of control
subjects’ performance). For the Schenkenberg test, we con-
sidered hemispatial neglect to be present when participants
exhibited a mean rightward deviation of greater than 1.53 cm.
B. Cancellation tasks. The Albert Test and the Star Cancel-
lation test were used. For both tests, we considered a cut-off
score of two omissions on the left hemispace of the paper.
C. Drawing. A drawing-copy test and the Clock Test of
drawing for memory were performed. A score was considered
pathological when left-sided elements of the drawing were
D. Reading task. We asked participants to read aloud eight
sentences of different lengths presented separately on a sheet
of paper (cut-off score: 2 errors).
In addition, the Mini Mental State Examination Test was per-
formed to assess possible cognitive decline. Patients were ex-
cluded if they scored below the cut-off of 24/30.
Clinical evaluation was supplemented by an assessment of mo-
tor, somatosensory, and visual deficit awareness, using the Bisiach,
Vallar, Perani, Papagno, and Berti (1986) questionnaire. Auditory
extinction was also assessed by delivering 10 tones unilaterally
(right and left) and 10 tones under a dichotic listening condition.
The tone duration was 500 ms, and auditory extinction was con-
sidered if the patient missed more than 60% of the left stimuli
under the dichotic condition.
Statistical Analysis
Mixed repeated measure ANOVAs were performed on the per-
centage of correct responses. Within-subject factors included:
Tone Series (short vs. long), Side of Standard Tone Presentation
(right vs. left), Time Offset (100, 200, and 300 ms). The between-
subjects factor was the Group (N,N, and HC).
For the point of subjective equivalence (PSE, for its calculation
see below), it was conducted a mixed repeated measure ANOVA
considering the standard tone (700 vs. 1,700) as within-subject
factor and the Group (N,N, and HC) as between-subjects
The assumption of sphericity was assessed using Mauchly’s
Test, and the Geisser-Greenhouse correction for the number of
degrees of freedom was adopted when necessary. Size effects are
reported as partial eta squared values (
Post hoc analyses were performed by applying the False Dis-
covery Rate (FDR) together with the Benjamini and Hochberg
(1995) procedure for multiple comparisons. This technique has the
advantage of controlling for Type I errors and is applicable for
both within- and between-subjects comparisons. Statistical analy-
ses were performed with SPSS (SPSS, Inc., Chicago) and the alpha
value for significance was set equal to 0.05.
The correct response percentages were analyzed to compare
between-group performance. We found a significant main effect of
Group [F(2, 19) 52.52, p.001
0.85]. Post hoc analyses
revealed that Npatients (62.4 18.4) scored significantly worse
than N(78.2 15.2, p.0001) and HC (85.2 14.1; p
.0001); moreover, Npatients were significantly worse than HC
A main effect of Tone Series [F(1, 19) 36.23, p.001,
0.66] was found. All participants exhibited better perfor-
mances for the short Tone Series (81.1 17.2) than for long ones
(60.5 17.4), but there was no difference between groups (no
significant interaction of Tone series and Group). The main effect
of Time Offset was also significant [F(1.98, 37.66) 49.28, p
0.72), demonstrating a linear effect as the Offset
between standard and test tones increased.
Interestingly, the interaction between Side of Presentation
Time Offset Group was statistically significant [F(2.94,
27.97) 4.51, p.01,
0.32]. Post hoc analyses showed
that the Npatients recorded performances that were signifi-
cantly weaker than HC for all the Time Offsets considered.
Namely, for the right side: at 100 ms (N⫹⫽
58.1 15.6, HC 73.2 6.9; p.03), 200 ms (N⫹⫽
67.9 16.6, HC 93.2 8.0; p.007), and 300 ms
(N⫹⫽66.7 21.7, HC 98.2 5.1; p.0009). For the left
side: at 100 ms (N⫹⫽49.7 9.7, HC 76.9 11.2; p.0006),
200 ms (N⫹⫽57.8 16.1, HC 95.1 5.8; p.0001), and
300 ms (N⫹⫽77.6 14.3, HC 94.3 7.8; p.002). Even
if the two groups (i.e., Nand HC) performed similarly for both
sides, higher differences were found on the left side; for this reason
the Side of Presentation Time Offset Group interaction was
significant. That is, the difference, on the right side, between N
and HC was 15.1 ms at 100 ms Time Offsets, and 30.5 ms at 200
ms Time Offsets. While on the left side these differences were
higher: 27.2 ms and 40.3 ms at 100 and 200 ms Time Offsets,
Moreover Nindividuals performed significantly worse than
Npatients for all Time Offsets ( p.05), whereas the N
performance metrics were not significantly different in terms of
Time Offset to those of HCs (see Figure 1).
Point of Subjective Equivalence (PSE)
We calculated the PSE, defined as the perceived duration (of the
test tone) in relation to the reference duration (of the standard
tone), for each participant. The PSE was calculated following this
method. First, we calculated the probability of the “test longer”
responses against the actual duration of the stimulus. The proba-
bility goes from 0 to 100%, where 50% stands for the subjective
perception of the stimulus duration equal to the test duration. Then,
data were fitted to a logistic function and PSE (in milliseconds)
was estimated for each participant trough the regression param-
eter (using the standard durations, such as 700 and 1,700 ms).
If the PSE is inferior to the standard tone duration it means that
there is an underestimation of the perceived test tone, and if the
PSE is longer an overestimation is assumed. So, the PSE estimates
the subjective perception of each participant when the tone is 700
or 1,700 ms long. For instance, if the standard tone duration is 700
ms and the PSE is 650 ms, this means that participant had per-
ceived the duration of the tone 50 ms shorter, indicating an
For the standard of 700 ms and the test on the right, the PSE for
the Npatients was 772 (81), 671 (26) for N, and 683
(31) for HC. When the test was presented on the left the PSE, or
the Npatients was 692 (81), 691 (26) for N, and 690
(31) for HC. The analysis showed a significant overestimation of
the duration (72 ms) of Npatients compared to N(29 ms,
p.03) and HC (17 ms, p.04), when the test tone was on the
right. No difference between groups was found when the test tone
was presented on the left.
For the standard of 1,700 ms and the test on the right, the PSE
for the Npatients was 1769 (94), 1628 (91) for Nand 1638
(105) for HC. When the test was presented on the left the PSE,
or the Npatients was 1667 (110), 1638 (126) for Nand
1634 (65) for HC. The analysis showed a significant overesti-
mation of the duration (69 ms) of Npatients compared to N
(72 ms, p.04) and HC (62 ms, p.04), when the test tone
was on the right. No difference between groups was found when
the test tone was presented on the left (see Figure 2).
Spearman’s rank correlation coefficients were calculated con-
sidering the spatial bias in line bisection and the N’s perfor-
mance in time discrimination task. For line bisection it was con-
sidered the spatial rightward bias from the geometric midpoint for
the three length of lines (5, 10 and 25 cm). It was considered the
percentage of correct responses for the three time offsets (100,
200, and 300 ms), when the test tone was delivered on the right and
the left side, respectively. Positive correlations between the per-
centage of correct responses for the time offset of 300 ms on the
right and the rightward bias in bisection of 10 cm (r.87) and
of 25 cm (r.93) lines were found. Negative correlations be-
tween the percentage of correct responses for the time offset of 300
ms on the left and the rightward bias in bisection of 10 cm (r
0.82) and of 25 cm (r⫽⫺0.81) lines were found. These results
indicate that in Nlarger the spatial bias poorer the performance
in the time discrimination task when the test tone was delivered on
the left, but not on the right.
In Npatients, PSE negatively correlated with the magnitude of
the rightward bias only when the test tone was presented on the left
(r⬎⫺0.71). This indicates that the larger is the spatial bias on line
bisection, the larger is the underestimation of the time duration on
the left side.
Recent evidence has suggested that numbers, space, and time
share a common cognitive mechanism and neural substrate in the
parietal cortex (Walsh, 2003). Distortion of space and numbers has
been previously demonstrated in brain damaged patients by several
studies (e.g., Hubbard et al., 2005; Zorzi, Priftis, & Umilta, 2002)
strengthening the idea of a direct relationship between the two.
Conversely, to the best of our knowledge, the relationship
between time and space has not been widely investigated in
patients with visuospatial deficits, such as hemispatial neglect
patients (Basso et al., 1996). In the current study, a time discrim-
ination task was performed with a group of neglect patients, and
the data were compared to a group of right-brain damaged patients
without spatial neglect and a group of HCs. In general, we con-
cluded that neglect patients were more severely impaired in terms
of time discrimination compared to both HCs and right-brain
damaged patients without visuospatial deficits. These results are
consistent with previous studies that investigated temporal pro-
cessing in neglect patients (for a review see Becchio & Bertone,
2006). These studies have suggested that neglect patients have
deficits in processing time information because of their inability to
integrate information across time or in temporal processing (e.g.,
Husain, Shapiro, Martin, & Kennard, 1997).
It was not found any effect of tone series between groups. All
the groups had a lower performance in processing long tones
(1,700 ms) in comparison to short tones (700 ms), but this effect
was of the same size in all groups.
Neglect patients performed worse than controls both when the
test tone was presented on the left and when it was presented on
the right. Only small differences in effect-size were found: neglect
patients performed worse when the test tone was on the left than on
the right for short time intervals (i.e., 100 and 200 ms). It is known
that, in neglect patients, left-side stimuli are often not reported or
undetected (Heilman, Watson, & Valenstein, 2005) because of the
right parietal damage and its consequential attentional impair-
ments. By assuming a parallelism between space and time repre-
sentation, we hypothesized that time discrimination might be more
severely impaired when the target stimuli were presented on the
left side, as left-sided targets are impaired in spatial processing.
Space and time processing are thought to share the same neural
network, namely the right parietal region (Bueti & Walsh, 2009;
Walsh, 2003), which is one of the typical lesion sites associated
Figure 1. Percentage of correct responses in the time discrimination task,
as a function of the side of test tone presentation. Bars display means and
standard errors. N⫹⫽patients with spatial neglect (n6); N⫺⫽patients
without spatial neglect (n8); HC healthy controls (n8).
with spatial neglect (Husain & Nachev, 2006). Conversely, our
behavioral results suggest that time discrimination is always im-
paired irrespective of the side of presentation.
However, when we looked at the qualitative aspect of the time
distortion, such as under- or overestimation, interesting results
were found. We calculate the PSE for each participant to see the
subjective estimation of the perceived time duration of the test
tone. It is supposed that shorter PSE respect to the standard tone is
consistent with an underestimation and vice versa. It was found
that Npatients have an overestimation of about 70 ms whereas
Nand controls showed underestimation, when the test tone was
presented on the right. Conversely, when the test tone was pre-
sented on the left the slope function of the PSE changed (it was
flatter than HC group), and no difference to HC for the PSE was
observed for N.
These results could be compatible with an impaired clock mech-
anism (Gibbon, Church, & Meck, 1984). The internal clock is an
accumulator that sums pulses produced by a pacemaker. The
output of the accumulator is compared to reference in the memory,
and time estimation is made. In this case, impaired attentional
resource in Naffects the accumulation resulting in a higher
production of the pulses, and consequently an overestimation. This
overestimation was observed when the test tone was on the right,
so not in the neglected space. So, it is not the case. How can this
overestimation on the right be explained? Beside the accumulator,
in the model of Gibbon et al. (1984) reference memory and
working memory are included. Reference memory is related to
the representation of the time and permits the comparison with the
output of the accumulator, while working memory allows the
temporal storing of the information. It is likely that one of these
two systems is affected in the Npatients. When the standard
tone is in the memory and its representation is distorted (i.e.,
smaller in N) the consequence is an overestimation of the test
tone perception, as showed by present results. The distortion of the
standard tone occurred in the neglected space and consequently the
test tone perceived on the right was altered, inducing an overesti-
mation on the right side, as our results shown. Interestingly, the
underestimation in controls mimics what it is classically found in
line bisection. Neurologically normal subjects bisect space during
line bisection systematically on the left of the geometrical mid-
point, a phenomenon called “pseudoneglect” (Jewell & McCourt,
2000). The same bias for time perception and spatial representation
suggests, to some extent, a common mechanism already in healthy
Basso et al. (1996) found an overestimation in the leftmost part
of right space, in which neglect was present as well. These oppo-
site results could be explained by the different methodology. We
presented the stimuli each to one ear, whereas Basso et al. (1996)
required classifying a shorter or longer stimulus after a phase of
training. Moreover in Basso et al. (1996) the stimuli were pre-
sented in the visual modality, while in our study we used auditory
modality. Alternatively these different results could be because of
the organization of the sensory modalities, that is, the time dis-
crimination of Nfor auditory material is less specific to one
hemisphere because a less lateralized representation of time is
present in the auditory space.
Even if different pattern of time estimation has been found in
our participants, it appeared that Nshowed lower performance in
time discrimination compared to Nand HC. So, our results may
also be explained in terms of a general deficit in temporal dynam-
ics (see Husain et al., 1997). When healthy participants are re-
quired to detect two serially presented targets, they need about 400
ms between the two targets to be able to report both. When neglect
patients are confronted with the same task, they exhibit a longer
attentional blink effect than HCs (Husain et al., 2001; Husain et al.,
1997). This suggests that neglect patients suffer from a deficit in
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Proportion of longer standard tone
Right side Left side
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Time offsets
N -
N +
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Proportion of longer standard tone
Right side Left side
0.5 0.5
Time offsets
-300 - 200 -100 +100 +200 +300
-300 -200 -100 +100 +200 +300
Proportion of longer standard tone
Right side Left side
0.5 0.5
Time offsets
N -
N +
Figure 2. PSE for each group in the time discrimination task, as a function of the side of test tone presentation.
N⫹⫽patients with spatial neglect (n6); N⫺⫽patients without spatial neglect (n8); HC healthy
controls (n8).
detecting stimuli over time. Neglect patients fail to correctly retain
the representation of the stimuli, and in turn they fail to compare
the various interval durations presented in the task. This may lead
to deficits in the estimation of time duration, as shown by our
Battelli, Walsh, Pascual-Leone, and Cavanagh (2008) also sug-
gest different role of the parietal lobe, the so called “when”
pathway. According to these authors the parietal lobe is involved
in the spatial attentional processing and this function is strongly
contralateral. Conversely, the control of the right parietal lobe over
temporal attention is bilateral. This bilateral control could be
impaired in Npatients, reflecting a lower performance in time
discrimination both in the right and in the left side of the space.
In general, we found that right-brain damaged patients without
neglect performed significantly worse than HCs but better than
spatial neglect patients. However, when the presentation side was
taken into account in our analyses, patients without neglect per-
formed as well as HCs did. This again confirms the interdepen-
dence of spatial and time codes in perception. Moreover, the
correlational analysis support that the larger is the rightward bias
in Nthe larger is the impairment in time discrimination.
We cannot specifically determine whether the lesion site was
related to performance, because only general data of structural
imaging are available of our patients. However, almost all our
neglect patients exhibited damage involving those temporo-pari-
etal regions that are related to spatial functions (Husain & Nachev,
2006). Even though right hemisphere involvement in time process-
ing remains under debate (Funnell, Corballis, & Gazzaniga, 2003;
Handy, Gazzaniga, & Ivry, 2003; Kagerer, Wittmann, Szelag, &
Steinbuchel, 2002), imaging studies in brain damaged patients
(Harrington & Haaland, 1999) have identified a right hemispheric
superiority in time perception, specifically involving the fronto-
parietal network. From a speculative point of view, this could
support he notion that time and space are not only functionally
linked, but they also share the same neural network.
In conclusion, the results of the present study support the exis-
tence of an overlapping perception of time and space. Neglect
patients, who are known to be impaired in spatial processing, also
exhibit impairment in terms of time discrimination. These data
support the hypothesis of a “distortion” of the representation in the
reference memory or impaired working memory in time process-
ing that is potentially located in the right parietal cortex, a neural
network involved in spatiotemporal processing of perception and
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Received February 17, 2010
Revision received August 11, 2010
Accepted August 12, 2010
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... To date, there has been relatively little investigation of perceptual timing within the stroke literature, and in particular with individuals following transient ischemic attack (TIA), where transient stroke symptoms resolve within 24 hours 33,34 . From the extant literature, findings have consistently demonstrated a gross underestimation of time interval in right-hemisphere damaged patients with neglect (RHD-N) 6,35-37 (see Supplementary Table for a summary of studies of perceptual timing after a stroke 6,[35][36][37][38][39][40][41]. While this underestimation has been frequently interpreted in the context of the pacemaker-accumulator model described above 7,15,16 , different suggestions have been proposed regarding the specific cause. ...
... While this underestimation has been frequently interpreted in the context of the pacemaker-accumulator model described above 7,15,16 , different suggestions have been proposed regarding the specific cause. On one end, the underestimation has been attributed to attentional deficits (reduced allocation of attention to time due to attentional resources being used for the external task at hand) resulting in a deceleration of the pacemaker 35,37 . On another end, impairments in spatially maintaining the representation of pulses in the accumulator (i.e., visual working memory deficits), or in comparing this temporary representation of pulses to reference memory, have also been suggested as plausible reasons 6,42 .In addition, within non-neglect stroke patients, only one study so far has revealed significantly impaired time estimation (as measured by duration discrimination of auditory tones) following right-hemisphere damage (RHD) 38 , while other studies have only demonstrated a similar trend following RHD 6,37 . ...
... On one end, the underestimation has been attributed to attentional deficits (reduced allocation of attention to time due to attentional resources being used for the external task at hand) resulting in a deceleration of the pacemaker 35,37 . On another end, impairments in spatially maintaining the representation of pulses in the accumulator (i.e., visual working memory deficits), or in comparing this temporary representation of pulses to reference memory, have also been suggested as plausible reasons 6,42 .In addition, within non-neglect stroke patients, only one study so far has revealed significantly impaired time estimation (as measured by duration discrimination of auditory tones) following right-hemisphere damage (RHD) 38 , while other studies have only demonstrated a similar trend following RHD 6,37 . This disparity in findings may be related to sample sizes, as evidenced by a larger stroke group in Harrington et al. 38 (see Supplementary Table). ...
Full-text available
Perception of the passage of time is essential for safe planning and navigation of everyday activities. Findings from the literature have demonstrated a gross underestimation of time interval in right-hemisphere damaged neglect patients, but not in non-neglect unilaterally-damaged patients, compared to controls. This study aimed to investigate retrospective estimation of the duration of a target detection task over two occasions, in 30 stroke patients (12 left-side stroke 15 right-side stroke, and 3 right-side stroke with neglect) and 10 transient ischemic attack patients, relative to 31 age-matched controls. Performances on visual short-term and working memory tasks were also examined to investigate the associations between timing abilities with residual cognitive functioning. Initial results revealed evidence of perceptual time underestimation, not just in neglect patients, but also in non-neglect unilaterally-damaged stroke patients and transient ischemic attack patients. Three months later, underestimation of time persisted only in left-side stroke and right-side stroke with neglect patients, who also demonstrated reduced short-term and working memory abilities. Findings from this study suggest a predictive role of residual cognitive impairments in determining the prognosis of perceptual timing abnormalities.
... The evolutionary paradigm can be regarded as the backdrop, which enables us to explain the high order questions such as, "Why and how did time perception develop as it did?" The anomalies can be potentially useful in showing us possible detrimental effects on evolutionary fitness when time perception is deficient (Calabria, 2011). ...
... The study consisted of patients with spatial neglect and a control group (individuals with normal visual fields). The results of the study conclude that participants with spatial neglect are significantly inhibited in judging the duration of the test sounds correctly (Calabria, 2011). Therefore, acoustic signals can be assumed to have played an important role in determining the evolutionary fitness of an individual (Barkow, 1996). ...
... In addition to the well-known spatial deficits, Neglect syndrome has further been related to impairments both in time estimation (e. g., Calabria et al., 2011;Danckert et al., 2007;Husain et al., 1997) and in the so-called 'the when parietal pathway' (Battelli et al., 2007;Batelli et al., 2008). This circuit is lateralized to the right parietal lobe and supports temporal processes mediated by attention, for example, the discrimination of two stimuli that occur at the same spatial location but at different time intervals. ...
... Regarding the relationship between Neglect syndrome, the parietal lobe dysfunction and temporal processing, several studies have shown that lesions in the right parietal cortex, more specific in the right temporo-parietal junction (TPJ), are related to an impaired execution in time estimation (Calabria et al., 2011;Danckert et al., 2007;Husain et al., 1997) and temporal order judgment -TOJ-tasks (Agosta et al., 2017;Berberovic et al., 2004;Husain et al., 2003;Roberts et al., 2012;Robertson et al., 1998). These neuropsychological studies also demonstrate the relation between the Neglect syndrome and these altered temporal processes (15 from 18 Neglect patients in Agosta et al., 2017; 18 from 25 patients in Roberts et al., 2012). ...
The right parietal cortex has been widely associated with a spatial orienting network. Its damage frequently produces the Neglect syndrome consisting in deficits in spatial attention to the left hemifield. Neglect has also been related to temporal deficits (such as the estimation of the duration of a stimulus or the discrimination of two stimuli that occur at the same spatial location but at different time intervals). Such attentional deficits have been much less studied in the temporal as compared to the spatial domain. The current research focused on the study of temporal attention processes in patients with Neglect syndrome, specifically, on temporal preparation. We recruited 10 patients with Neglect syndrome, 10 patients without Neglect syndrome, as well as 11 healthy individuals. Each participant completed an experimental task which measures three main temporal preparation effects described in the literature: Temporal orienting and Foreperiod effects (both related to control mechanisms and prefrontal areas) and Sequential effects (automatic in nature and related to parietal and subcortical structures). The results showed a deficit in the sequential effects only in those patients who suffered from Neglect syndrome. The results suggest a causal relation between Neglect syndrome and the automatic mechanisms of temporal preparation. Since our sample of Neglect patients had suffered lesions mainly in the parietal cortex, the results are discussed taking into account the role of the parietal lobe in the processing of time and the models explaining sequential effects.
... Furthermore, perceived time durations can be distorted by auditory, visual, tactile and multisensory interactions (Sanders & Cairns, 2010;van Wassenhove, Buonomano, Shimojo & Shams, 2008). Neuropsychological studies report that the mental representation of time could be linked to spatial representation and share common cortical networks (Calabria, Jacquin-Courtois, Miozzo, Rossetti, Padovani, Cotelli & Miniussi, 2011). ...
Virtual Reality Head Mounted Displays (VR HMDs) offer highly immersive experiences that may alter users’ awareness and perception of the “real-world”. This paper investigates users’ perception of short duration (<5 minutes) time periods during simulated scenarios between two different simulation mediums. Fifty participants (Age: M=29.2 years; SD=10.7 years; 15 Females; 35 Males) were randomly assigned to one of two groups: (i) VR HMD or (ii) desktop computer configuration, where they performed identical searching tasks within a virtual environment three consecutive times. After each virtual session participants were asked to verbally report their perception of time duration. Results reveal that participants across both groups overestimated time duration in virtual environments by an average of 20.3%. As participants gained experience performing the task repeatedly across three consecutive attempts, their task completion time reduced (i.e. learning effect). However, participants’ accuracy of time perception continued to be consistently overestimated across both conditions.
... Among the parietal lobe structures contributing to ATOM as a "general magnitude system", the inferior parietal lobule and the posterior parietal cortex might play an especially critical role. These structures have not only been discussed in the context of integrating temporal and spatial information (Calabria et al., 2011), but also with respect to their role in multisensory integration (Assmus et al., 2003;Bolognini, Miniussi, Savazzi, Bricolo, & Maravita, 2009). A comprehensive and well-established model of spatial attention (Corbetta & Shulman, 2002) differentiates partially segregated networks, one of which is lateralized to the right hemisphere. ...
Space, numbers and time share similar processing mechanisms mediated by parietal cortex. In parallel to the spatial representation of numbers along a horizontal line, temporal information is mapped on a horizontal axis with short intervals (and the past) represented to the left of long intervals (and the future). Little is known about the representation of time in the presence of visuo-spatial deficits. We here report two experiments on the comparative judgment of time. Experiment 1 required patients with left-sided neglect to indicate which of two consecutively presented silent intervals was longer. Their judgments were better if the first interval was longer and they judged the first interval longer on trials in which the two intervals were equally long. These results were not present in right-hemispheric damaged patients without neglect and healthy controls. They are in line with a previously reported finding in a single patient with neglect, but not readily compatible with findings of neglect patients’ comparative length judgments. In Experiment 2, healthy participants’ performance on an identical task improved for trials with a first-longer interval after caloric vestibular stimulation (CVS) of the right ear with warm water.
... Space and time are tightly interwoven dimensions in the brain, as evidenced by psychophysical [1 -4], neuropsychological [5][6][7][8] and neuroimaging accounts [9]. Spatial and temporal information are known to interact in a variety of different contexts [10 -14]. ...
... This region, corresponding to the superior longitudinal fasciculus (SLF), has been recently associated with spatial attention [57][58][59] and spatial orientation [60,61], and is involved in the genesis of unilateral neglect in focal brain damaged patients [62]. Previous findings in neglect patients supported the idea that mental representation of time would follow a spatially-oriented "mental time line" accessible by spatial attention mechanisms [16,63,64], linking left spatial neglect with temporal errors [65]. However, seven of our patients had clinical evidence of left spatial neglect, as it could be predicted on the basis of the lesion pattern, but we did not observe differences in the distribution of overor under-estimation in RBD patients with or without spatial neglect, or even in patients with right or left hemisphere lesions. ...
The aim of the study was to identify the anatomical bases involved in the subjective experience of time, by means of a voxel based symptom-lesion mapping (VLSM) study on patients with focal brain damage. Thirty-three patients (nineteen with right-hemisphere lesions −RBD, and fourteen with left lesion- LBD) and twenty-eight non-neurological controls (NNC) underwent the semi-structured QUEstionnaire for the Subjective experience of Time (QUEST) requiring retrospective and prospective judgements on self-relevant time intervals. All participants also completed tests to assess general cognitive functioning and two questionnaires to evaluate their emotional state. Both groups of brain-damaged patients achieved significantly different scores from NNC on the time performance, without differences between RBD and LBD. VLSM showed a cluster of voxels located in the right inferior parietal lobule significantly related to errors in the prospective items. The lesion subtraction analysis revealed two different patterns possibly associated with errors in the prospective items (the right inferior parietal cortex, rolandic operculum and posterior middle temporal gyrus) and in the retrospective items (superior middle temporal gyrus, white matter posterior to the insula).
... Over the past decade, however, research has begun to demonstrate that neglect is not limited to spatial deficits alone. In fact, various forms of non-spatial, temporal deficits of attention have been demonstrated post-stroke, an example being the inability to orient attention to time properties, thus resulting in perceptual timing inaccuracies (e.g., underestimation of the passage of time; Harrington et al., 1998;Morin et al., 2005;Danckert et al., 2007;Merrifield et al., 2010;Calabria et al., 2011;Low et al., 2016). Overall, these studies have consistently suggested a role for a hypothetical internal clock (Treisman, 1963;Meck and Benson, 2002) that becomes compromised following a stroke, causing an inability to register the passage of time pulses as fast as the passage of real-time itself. ...
Full-text available
In recent years, evidence has emerged to suggest abnormal temporal dynamics of attentional processing in stroke patients, especially those presenting with neglect symptoms. However, there has been little profiling of the nature and extent of such temporal anomalies. In addition, many paradigms currently used to measure the time required to deploy visual attention in stroke require a psychomotor response, and may therefore confound performance outcomes. Thus, the aim of this systematic review was to identify and evaluate studies that have employed non-motor psychophysical paradigms to characterize the temporal deployment of visual attention in space. A total of 13 non-motor psychophysical studies were identified, in which stimulus exposure times were manipulated to measure the time course of attentional deployment. Findings suggest that prolonged attentional deployment thresholds are more likely to occur with lesions within more ventral areas of the fronto-parietal network, irrespective of whether patients presented with neglect. Furthermore, this deficit was greater following right-hemispheric lesions, suggesting a dominant role for the right-hemisphere in facilitating efficient deployment of attention. These findings indicate that area and hemisphere of lesion may serve as putative markers of attentional deployment efficiency. In addition, findings also provide support for using non-motor psychophysical paradigms as a more rigorous approach to measuring and understanding the temporal dynamics of attention.
... Two studies have shown that neglect patients present selective deficits also when brief time durations have to be categorized with respect to a standard. In a first one [20], RHD patients with neglect performed significantly worse than RHD patients without neglect and healthy controls, irrespective of the duration of the standard tone and without any interval-specific deficit. In a second study [21], patients with more severe neglect showed a disrupted time-space association for short durations only, as if these were ignored because of a left-to-right ordering. ...
Full-text available
Recent research has led to the hypothesis that events which unfold in time might be spatially represented in a left-to-right fashion, resembling writing direction. Here we studied fourteen right-hemisphere damaged patients, with or without neglect, a disorder of spatial awareness affecting contralesional (here left) space processing and representation. We reasoned that if the processing of time-ordered events is spatial in nature, it should be impaired in the presence of neglect and spared in its absence. Patients categorized events of a story as occurring before or after a central event, which acted as a temporal reference. An asymmetric distance effect emerged in neglect patients, with slower responses to events that took place before the temporal reference. The event occurring immediately before the reference elicited particularly slow responses, closely mirroring the pattern found in neglect patients performing numerical comparison tasks. Moreover, the first item elicited significantly slower responses than the last one, suggesting a preference for a left-to-right scanning/representation of events in time. Patients without neglect showed a regular and symmetric distance effect. These findings further suggest that the representation of events order is spatial in nature and provide compelling evidence that ordinality is similarly represented within temporal and numerical domains.
We explored the effect of gravity on the accuracy for estimating durations of 3.5, 7, and 14 s. Experiments were performed on board an Airbus A310 during parabolic flights eliciting repeated exposures to short periods of 0, 1, and 1.8 g. Two methods for obtaining duration estimates were used, reproduction and production of duration, in two conditions: a control counting condition and a concurrent reading condition. Simple reaction times were also measured to assess attention. The results showed that the temporal accuracies during the reproduction task in the concurrent reading condition were significantly underestimated in 0 g compared with 1 g. Reaction times were also longer in 0 g. However, there was no difference in duration estimates in the production tasks. These results suggest that the temporal underestimation in 0 g is caused by decreased selective attention and impaired retrieval of information in episodic memory.
Full-text available
The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses – the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferroni-type procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
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This study investigated time, numerosity and space processing in a patient (CB) with a right hemisphere lesion. We tested whether these magnitude dimensions share a common magnitude system or whether they are processed by dimension-specific magnitude systems. Five experimental tasks were used: Tasks 1-3 assessed time and numerosity independently and time and numerosity jointly. Tasks 4 and 5 investigated space processing independently and space and numbers jointly. Patient CB was impaired at estimating time and at discriminating between temporal intervals, his errors being underestimations. In contrast, his ability to process numbers and space was normal. A unidirectional interaction between numbers and time was found in both the patient and the control subjects. Strikingly, small numbers were perceived as lasting shorter and large numbers as lasting longer. In contrast, number processing was not affected by time, i.e. short durations did not result in perceiving fewer numbers and long durations in perceiving more numbers. Numbers and space also interacted, with small numbers answered faster when presented on the left side of space, and the reverse for large numbers. Our results demonstrate that time processing can be selectively impaired. This suggests that mechanisms specific for time processing may be partially independent from those involved in processing numbers and space. However, the interaction between numbers and time and between numbers and space also suggests that although independent, there maybe some overlap between time, numbers and space. These data suggest a partly shared mechanism between time, numbers and space which may be involved in magnitude processing or may be recruited to perform cognitive operations on magnitude dimensions.
Full-text available
The development of sub-disciplines within cognitive neuroscience follows common sense categories such as language, audition, action, memory, emotion and perception among others. There are also well-established research programmes into temporal perception, spatial perception and mathematical cognition that also reflect the subjective impression of how experience is constructed. There is of course no reason why the brain should respect these common sense, text book divisions and, here, we discuss the contention that generalized magnitude processing is a more accurate conceptual description of how the brain deals with information about time, space, number and other dimensions. The roots of the case for linking magnitudes are based on the use to which magnitude information is put (action), the way in which we learn about magnitudes (ontogeny), shared properties and locations of magnitude processing neurons, the effects of brain lesions and behavioural interference studies. Here, we assess this idea in the context of a theory of magnitude, which proposed common processing mechanisms of time, space, number and other dimensions.
The representation of time and space are closely linked in the cognitive system. Optokinetic stimulation modulates spatial attention in healthy subjects and patients with spatial neglect. In order to evaluate whether optokinetic stimulation could influence time perception, a group of healthy subjects performed "time-comparison" tasks of sub- and supra-second intervals before and after leftward or rightward optokinetic stimulation. Subjective time perception was biased by the direction of optokinetic stimulation. Rightward optokinetic stimulation induced an overestimation of time perception compared with baseline and leftward optokinetic stimulation. These results indicate a directional bias in time perception induced by manipulation of spatial attention and could argue for a mental linear representation of time intervals.
An exhaustive qualitative (vote-counting) review is conducted of the literature concerning visual and non-visual line bisection in neurologically normal subject populations. Although most of these studies report a leftward bisection error (i.e., pseudoneglect), considerable between-study variability and inconsistency characterize this literature. A meta-analysis of this same literature is performed in which the total quantitative data set, comprising 73 studies (or sub-studies) and 2191 subjects, is analyzed with respect to 26 performance factors. The meta-analytic results indicate a significant leftward bisection error in neurologically normal subjects, with an overall effect size of between -0.37 and -0.44 (depending on integration method), which is significantly modulated to varying degrees by a number of additional task or subject variables. For example, visual bisection tasks, midsagittal-pointing tasks and tactile bisection tasks all lead to leftward errors, while kinesthetic tasks result in rightward errors. Tachistoscopic forced-choice testing methods reveal much greater estimates of bisection error (effect size = -1.32) than do manual method-of-adjustment procedures (effect size= -0.40). Subject age significantly modulates line bisection performance such that older subjects err significantly rightward compared to younger subjects, and to veridical line midpoint. Male subjects make slightly larger leftward errors than do female subjects. Handedness has a small effect on bisection errors, with dextrals erring slightly further to the left than sinistral subjects. The hand used to perform manual bisection tasks modulated performance, where use of the left hand lead to greater leftward errors than those obtained using the right hand. One of the most significant factors modulating bisection error is the direction in which subjects initiate motor scanning (with either eye or hand), where a left-to-right scan pattern leads to large leftward errors while a right-to-left scan pattern leads to rightward errors.
Previous studies have demonstrated the involvement of spatial codes in the representation of time and numbers. We took advantage of a well-known spatial modulation (prismatic adaptation) to test the hypothesis that the representation of time is spatially oriented from left to right, with smaller time intervals being represented to the left of larger time intervals. Healthy subjects performed a time-reproduction task and a time-bisection task, before and after leftward and rightward prismatic adaptation. Results showed that prismatic adaptation inducing a rightward orientation of spatial attention produced an overestimation of time intervals, whereas prismatic adaptation inducing a leftward shift of spatial attention produced an underestimation of time intervals. These findings not only confirm that temporal intervals are represented as horizontally arranged in space, but also reveal that spatial modulation of time processing most likely occurs via cuing of spatial attention, and that spatial attention can influence the spatial coding of quantity in different dimensions.
The perception of events in space and time is at the root of our interactions with the environment. The precision with which we perceive visual events in time enables us to act upon objects with great accuracy and the loss of such functions due to brain lesions can be catastrophic. We outline a visual timing mechanism that deals with the trajectory of an object's existence across time, a crucial function when keeping track of multiple objects that temporally overlap or occur sequentially. Recent evidence suggests these functions are served by an extended network of areas, which we call the 'when' pathway. Here we show that the when pathway is distinct from and interacts with the well-established 'where' and 'what' pathways.