This work concerns the investigation of executive functions in patients with focal brain lesion. In order to identify the underlying substrates for executive functions, 54 patients with focal cortical (n=30), subcortical (n=13) and cerebellar damage (n=10) (M=9; F=1) in the age range of 24-65 years with a minimum of Class V education have been investigated. The patients were admitted to the Department of Neuromedicine of Bangur Institute of Neurology, Calcutta. Each patient with focal lesion was matched with a healthy normal subject controlling for age and education. The socio-economic background was also taken into consideration. Controls were selected from the families of other patients admitted to the institution and also from individuals who volunteered to act as controls. Here too, rigid criteria have been followed to select the normals. Mini Mental State Examination (MMSE) and General Health Questionnaire (GHQ) were administered to screen out the neurological and psychiatric abnormalities in selection of normal control and Wisconsin Card Sorting Test (WCST) was administered to find out the executive function, in terms of set-shifting ability. Since standard anatomical groupings can obscure more specific brain-behavior relations, group-comparison design does not always allow determination of the effective lesion responsible for a particular deficit (Godefroy et al., 1998). The Classification and Regression Tree (CART) analysis has been used to determine the brain-behavior relationships. The result reveals that the frontal lobes are essential determinants of set-shifting capacity. However, for optimal execution of set-shifting function, the frontal lobes require participation of other cortical, subcortical and cerebellar regions. The result has been discussed in the light of the existing theories and research reports.
"The orbitofrontal cortex in rhesus monkeys is also involved in associative learning, and processes reward and affect information (Meunier et al., 1997; Wallis and Miller, 2003). In humans, fMRI studies using normal controls, patients with frontal brain lesions, and patients with psychiatric illnesses related to frontal lobe dysfunction, such as schizophrenia, have also demonstrated a correlation between frontal lobe activity and WCST performance (Rogers et al., 2000; Monchi et al., 2001; Bonilha et al., 2008; Mukhopadhyay et al., 2008). In addition, it is important to note the involvement of cerebellar areas in the present cognitive task, as it is likely that the contribution of other cortical and cerebellar regions is critical for optimal functioning in this cognitive domain (Berman et al., 1995; Moore et al., 2009). "
[Show abstract][Hide abstract] ABSTRACT: The aged rhesus macaque exhibits brain atrophy and behavioral deficits similar to normal aging in humans. Here we studied the association between cognitive and motor performance and anatomic and microstructural brain integrity measured with 3T magnetic resonance imaging in aged monkeys. About half of these animals were maintained on moderate calorie restriction (CR), the only intervention shown to delay the aging process in lower animals. T1-weighted anatomic and diffusion tensor images were used to obtain gray matter (GM) volume and fractional anisotropy (FA) and mean diffusivity (MD), respectively. We tested the extent to which brain health indexed by GM volume, FA, and MD were related to executive and motor function, and determined the effect of the dietary intervention on this relationship. We hypothesized that fewer errors on the executive function test and faster motor response times would be correlated with higher volume, higher FA, and lower MD in frontal areas that mediate executive function, and in motor, premotor, subcortical, and cerebellar areas underlying goal-directed motor behaviors. Higher error percentage on a cognitive conceptual shift task was significantly associated with lower GM volume in frontal and parietal cortices, and lower FA in major association fiber bundles. Similarly, slower performance time on the motor task was significantly correlated with lower volumetric measures in cortical, subcortical, and cerebellar areas and decreased FA in several major association fiber bundles. Notably, performance during the acquisition phase of the hardest level of the motor task was significantly associated with anterior mesial temporal lobe volume. Finally, these brain-behavior correlations for the motor task were attenuated in CR animals compared to controls, indicating a potential protective effect of the dietary intervention.
"Moreover, many clinical studies show that damage in non-frontal (Leskela et al., 1999; van den Broek, Bradshaw, & Szabadi, 1993) or diffuse damage in frontal and non-frontal regions (Anderson, Damasio, Jones, & Tranel, 1991; Axelrod et al., 1996) both affect WCST performance. More specifically , many authors have reported that damage to temporal (Corcoran & Upton, 1993; Giovagnoli, 2001; Hermann, Wyler, & Richey, 1988; Horner, Flashman, Freides, Epstein, & Bakay, 1996; Strauss, Hunter, & Wada, 1993), subcortical (Mukhopadhyay et al., 2008), hippocampal (Corcoran & Upton, 1993; Giovagnoli, 2001; Igarashi et al., 2002), and even cerebellar regions (Mukhopadhyay et al., 2008) cause similar impairments on WCST performance as those subsequent to frontal lobe lesions. 3. Review of neuroimaging studies Modern functional neuroimaging techniques have been used in many studies to describe changes in brain activation during WCST performance. "
[Show abstract][Hide abstract] ABSTRACT: For over four decades the Wisconsin Card Sorting Test (WCST) has been one of the most distinctive tests of prefrontal function. Clinical research and recent brain imaging have brought into question the validity and specificity of this test as a marker of frontal dysfunction. Clinical studies with neurological patients have confirmed that, in its traditional form, the WCST fails to discriminate between frontal and non-frontal lesions. In addition, functional brain imaging studies show rapid and widespread activation across frontal and non-frontal brain regions during WCST performance. These studies suggest that the concept of an anatomically pure test of prefrontal function is not only empirically unattainable, but also theoretically inaccurate. The aim of the present review is to examine the causes of these criticisms and to resolve them by incorporating new methodological and conceptual advances in order to improve the construct validity of WCST scores and their relationship to prefrontal executive functions. We conclude that these objectives can be achieved by drawing on theory-guided experimental design, and on precise spatial and temporal sampling of brain activity, and then exemplify this using an integrative model of prefrontal function [i.e., Miller, E. K. (2000). The prefrontal cortex and cognitive control. Nature Reviews Neuroscience, 1, 59-65.] combined with the formal information theoretical approach to cognitive control [Koechlin, E., & Summerfield, C. (2007). An information theoretical approach to prefrontal executive function. Trends in Cognitive Sciences, 11, 229-235.].
Brain and Cognition 04/2009; 71(3):437-51. DOI:10.1016/j.bandc.2009.03.005 · 2.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The objective of this study is to identify the clinical, neuropsychological, neuropsychiatric, and functional variables that correlate with metacognitive self-awareness (SA) in severe traumatic brain injury (TBI) outpatients and to assess the influence of the same variables on the sensory-motor, cognitive, and behavioral-affective indicators of SA. This cross-sectional observational study evaluated 37 outpatients from May 2006 to June 2007 in a neurorehabilitation hospital on the basis of the following inclusion criteria: (1) age 8); (3) posttraumatic amnesia (PTA) resolution; (4) capacity to undergo formal psychometric evaluation despite cognitive and sensory-motor deficits; (5) absence of aphasia; (6) availability of informed consent. A neuropsychological battery was used to evaluate attention, memory, and executive functions. SA was assessed by the awareness questionnaire (AQ), administered to both patients and relatives. Decreased metacognitive self-awareness is significantly correlated with increased problems in some components of executive system, even when the AQ subscales were considered separately. The significant correlation found between some components of executive system and metacognitive self-awareness confirmed the importance of addressing this issue to treat SA contextually in the rehabilitation of executive functions.
Journal of the International Neuropsychological Society 10/2008; 14(5):862-8. DOI:10.1017/S1355617708081125 · 2.96 Impact Factor
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