Marina Pavlovskaya

Tel Aviv University | TAU · Department of Physiology and Pharmacology

Visual scenes are too complex for one to immediately perceive all their details. As suggested by Gestalt psychologists, grouping similar scene elements and perceiving their summary statistics provides one shortcut for evaluating scene gist. Perceiving ensemble statistics overcomes processing, attention, and memory limits, facilitating higher-order...

Previous studies have demonstrated a complex relationship between ensemble perception and outlier detection. We presented two array of heterogeneously oriented stimulus bars and different mean orientations and/or a bar with an outlier orientation, asking participants to discriminate the mean orientations or detect the outlier. Perceptual learning w...

A bombardment of information overloads our sensory, perceptual and cognitive systems, which must integrate new information with memory of past scenes and events. Mechanisms employed to overcome sensory system bottlenecks include selective attention, Gestalt gist perception, categorization, and the recently investigated ensemble encoding of set summ...

Visual scenes are too complex to perceive immediately in all their details. Two strategies (among others) have been suggested as providing shortcuts for evaluating scene gist before its details: (a) Scene summary statistics provide average values that often suffice for judging sets of objects and acting in their environment. Set summary perception...

Background: Patients with Balint syndrome following bilateral parietal damage are typically described as being unable to perceive multiple objects simultaneously, preventing them from understanding the visual scene despite correct identification of individual visual objects (simultanagnosia). We report observations with DP, a patient with a rare st...

In the framework of Reverse Hierarchy Theory it was suggested that initial vision at a glance brings the gist of the scene to conscious perception using explicit high cortical level representations, which are initially built by implicit bottom-up processing (Hochstein & Ahissar, 2002). Only later return to lower cortical level representations intro...

The syndrome of unilateral spatial neglect (USN) after right-hemisphere damage is characterized by failure of salient left-sided stimuli to activate an orienting response, attract attention, and gain access to conscious awareness. The explicit failure processing left-sided visual information is not uniform, however, and patients seem to be more suc...

Background / Purpose: People rapidly judge mean size of a set of circles, suggesting pre-attentive processing of statistical properties (1). Can neglect patients process statistical properties in their neglected field? Main conclusion: We conclude that neglect patients perform weighted averages across sides, giving partial-weight to left-side,...

Perceptual learning involves modification of cortical processes so that transfer to new task variants depends on neuronal representation overlap. Neuron selectivity varies with cortical level, so that the degree of transfer should depend on training-induced modification level. We ask how different can stimuli be, how far apart can their representat...

Hemispatial neglect is considered to be a disorder, which is primarily related to space. Inability to allocate attention properly to spatial-coded stimuli is of its essence. Recent evidence shows that hemispatial neglect might incorporate impairment in temporal attention as well as in spatial attention. For example, it was found that extreme elonga...

Previously, we found hemispheric differences when testing feature search with arrays wholly in one hemifield (Pavlovskaya et al., Spatial Vision, 2001), rather than testing with central arrays and lateral target elements. In parallel, Ahissar & Hochstein (Nature, 1997) found that perceptual learning transfer across position or orientation depends o...

Chong and Treisman (2003, 2005, 2008) found that people judge the mean size of a set of circles as quickly and accurately as that of a single item, suggesting that statistical properties may be processed without focused attention. The lack of awareness of left-side input in cases of Unilateral Spatial Neglect (USN) has been attributed to an inabili...

Background: Differences in perceptual learning transfer may be related to the cerebral sites of modification due to experience: hard-condition tasks are seen as requiring low-level (specific) representations while easy-condition tasks are performed using high cortical level mechanisms alone (Ahissar & Hochstein, Nature, 1997). As an example, we rec...

Unilateral spatial neglect (USN) patients show reduced contrast sensitivity on their contralesional side and often miss their non-salient stimuli. What their subjective experience is when successfully reporting a stimulus remains unclear. Here, we report that despite large contrast sensitivity differences between the sides, the relative attenuation...

To investigate whether the expression of visual extinction is dependent upon the contralesional low saliency existing in neglect, we tested stroke patients with neglect and extinction, as well as normal controls, on detection of a peripheral Gabor patch, while a competing patch was presented simultaneously on the other side. To compensate for uneve...

We find a spatially asymmetric allocation of attention in patients with traumatic brain injury (TBI) despite the lack of obvious asymmetry in neurological indicators. Identification performance was measured for simple spatial patterns presented briefly to a locus 5 degrees into the left or right hemifield, after precuing attention to the same (ipsi...

We found spatially asymmetric allocation of attention in patients with traumatic brain injury (TBI) without overt asymmetry on neurological examination. The possible effect of Methylphenidate in reducing this asymmetry is evaluated in the current research. Psychophysical study using a visual spatial attention task. Identification rates were measure...

Unilateral spatial neglect (USN) is considered to be an attention deficit, which is primarily related to space. Recent evidence points to the relevance of non-spatially lateralized mechanisms, with impairments found in rapid stimulus presentation conditions. Here we used the phenomenon of binocular rivalry (BR) to explore a non-spatial deficit over...

We address two longstanding conflicts in the visual search and unilateral neglect literature by studying feature and conjunction search performance of neglect patients using laterally presented search arrays. The first issue relates to whether feature search is performed independently of attention, or rather requires “spread attention”. If feature...

Psychostimulant medication such as methylphenidate (Ritalin) is generally used in traumatic brain-injured (TBI) patients in an attempt to improve global attention and arousal. We studied a possible effect of Ritalin on the efficiency of selective attention in four TBI patients by comparing the identification rates of prelearned patterns before, dur...

Feature search for a light bar with one orientation (or color) embedded in an array of bars with a very different orientation (or color) is quick, easy and independent of the number of array elements. In contrast, search for a conjunction target has a linear response time dependence on the number of distractors. Training can improve performance of...

Extinction is manifested in conditions of bilateral simultaneous stimulation, as a failure to detect the stimulus contra-lateral to the side of a cerebral lesion, while the same stimulus is correctly detected there when presented in isolation. The phenomenon is usually interpreted in terms of impaired mobilization of attention from an attended to a...

Visual extinction is a common, poorly understood, consequence of unilateral cerebral damage, where a patient fails to detect one of two simultaneously presented stimuli (the one more contralateral to the lesion), despite the fact that each stimulus is correctly detected when presented in isolation. The phenomenon implies a failure of shifting atten...

The present research examines the effect of spatial (object-centered) attentional constraints on pattern recognition. Four normal subjects and two right-hemisphere-damaged patients with left visual neglect participated in the study. Small, letterlike, prelearned patterns served as stimuli. Short exposure time prevented overt scanpaths during stimul...

Subjects were tested on orientation and colour pop-out tasks. Orientation pop-out stimuli were 3 × 3, 5 × 5, or 7 × 7 arrays of vertical light (white) bars (on a black background) with a target element of diagonal (45°) orientation (present on half of the trials). Colour pop-out stimuli consisted of 60° oriented bars with blue distractor and yellow...

The strategy for visual information processing must vary with the specific situation. We assume that in recognition of pre-learnt letter-like patterns under time-pressure conditions, mechanisms of selective attention are involved. We propose that, with simple stimuli, foveation is to the luminance centroids of such patterns, and if normally the lat...