Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2013
This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in... more This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in a sample of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) veterans referred for mild traumatic brain injury (mTBI). Three clusters were extracted, two of which were characterized by level of performance and the third with a unique performance pattern characterized by slow performance on the TMT B (Low B). Clusters did not differ on demographic or psychiatric variables. The Above Average cluster had better performance on measures of processing speed, working memory, and phonemic fluency compared with the Low B cluster. Results suggest that a subset of patients with mTBI perform poorly on TMT B, which subsequently predicts poorer cognitive functioning on several other neuropsychological measures. This subset may be vulnerable to cognitive changes in the context of mTBI and multiple comorbidities while a number of other patients remain cognitively unaf...
There is increasing evidence that schizophrenia (SZ) and bipolar disorder (BD) share a number of ... more There is increasing evidence that schizophrenia (SZ) and bipolar disorder (BD) share a number of cognitive, neurobiological, and genetic markers. Shared features may be most prevalent among SZ and BD with a history of psychosis. This study extended this literature by examining reinforcement learning (RL) performance in individuals with SZ (n = 29), BD with a history of psychosis (BD+; n = 24), BD without a history of psychosis (BD-; n = 23), and healthy controls (HC; n = 24). RL was assessed through a probabilistic stimulus selection task with acquisition and test phases. Computational modeling evaluated competing accounts of the data. Each participant's trial-by-trial decision-making behavior was fit to 3 computational models of RL: (a) a standard actor-critic model simulating pure basal ganglia-dependent learning, (b) a pure Q-learning model simulating action selection as a function of learned expected reward value, and (c) a hybrid model where an actor-critic is "augment...
Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2014
Low IQ has recently been shown to predict effort test failure in healthy and neurological populat... more Low IQ has recently been shown to predict effort test failure in healthy and neurological populations. Although low IQ is common in schizophrenia (SZ), its effect on effort test performance remains unclear. Participants included 60 outpatients with SZ and 30 demographically matched healthy controls (CN) who received a battery of neuropsychological tests. Insufficient effort was calculated using the Digit Span Age-Corrected Scaled Score Effort Index and the Finger Tapping Effort Index. A total of 33.3% SZ and 6.7% CN fell below the Digit Span Age-Corrected Scaled Score Effort Index cut-off χ(2)(1, 89) = 7.70, p < 0.01, and 35.7%SZ and 3.3% CN fell below the Finger Tapping Effort Index cut-off χ(2)(1, 85) = 11.10, p < 0.001. Low IQ is a significant predictor of falling below effort cut-off scores for indices embedded in standard neuropsychological tests. IQ may complicate the interpretation of effort testing in SZ patients who may have low motivation, but are not feigning cognit...
A comparison was made among participants with schizophrenia and those with structural lateralized... more A comparison was made among participants with schizophrenia and those with structural lateralized or diffuse brain damage in order to determine the extent to which the cognitive profile of the schizophrenia sample resembled the profiles obtained from patients with left-hemisphere, right-hemisphere, and diffuse brain damage. The Halstead-Reitan Neuropsychological Battery was used as the testing procedure. The data were subjected to discriminant analysis in order to obtain frequencies of predicted classification of the participants with schizophrenia into schizophrenia, left-hemisphere, right-hemisphere, and diffuse groups. Half of the participants with schizophrenia were classified into the schizophrenia group. The other half was evenly distributed across the left-hemisphere, right-hemisphere, and diffuse brain damage groups. There was not a disproportionately large number of participants classified into the left-hemisphere group. Comparisons among these four predicted groups were ac...
The authors' goal was to determine whether cognitively impaired patients with schizophrenia e... more The authors' goal was to determine whether cognitively impaired patients with schizophrenia exhibit age-related cognitive declines similar to those of patients with schizophrenia who do not have substantial cognitive impairment. Correlation coefficients were computed between age and the Average Impairment Rating, a summary index of cognitive ability, in a group of 77 patients with schizophrenia. These patients were clustered into two groups: one with near-normal cognitive function (N=51) and one with severely impaired cognitive function (N=26). A group of patients with senile dementia (N=21) and another comparison group of nonschizophrenic patients (N=299) were used as reference groups. There were significant correlations between age and the Average Impairment Rating in all groups except the cognitively impaired patients with schizophrenia, in which a zero-order correlation was obtained. Patients with schizophrenia who have substantial cognitive impairment do not have the signif...
Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2013
This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in... more This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in a sample of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) veterans referred for mild traumatic brain injury (mTBI). Three clusters were extracted, two of which were characterized by level of performance and the third with a unique performance pattern characterized by slow performance on the TMT B (Low B). Clusters did not differ on demographic or psychiatric variables. The Above Average cluster had better performance on measures of processing speed, working memory, and phonemic fluency compared with the Low B cluster. Results suggest that a subset of patients with mTBI perform poorly on TMT B, which subsequently predicts poorer cognitive functioning on several other neuropsychological measures. This subset may be vulnerable to cognitive changes in the context of mTBI and multiple comorbidities while a number of other patients remain cognitively unaf...
Recent studies have examined heterogeneous neuropsychological outcomes in childhood traumatic bra... more Recent studies have examined heterogeneous neuropsychological outcomes in childhood traumatic brain injury (TBI) using cluster analysis. These studies have identified homogeneous subgroups based on tests of IQ, memory, and other cognitive abilities that show some degree of association with specific cognitive, emotional, and behavioral outcomes, and have demonstrated that the clusters derived for children with TBI are different from those observed in normal populations. However, the extent to which these subgroups are stable across abilities has not been examined, and this has significant implications for the generalizability and clinical utility of TBI clusters. The current study addressed this by comparing IQ and memory profiles of 137 children who sustained moderate-to-severe TBI. Cluster analysis of IQ and memory scores indicated that a four-cluster solution was optimal for the IQ scores and a five-cluster solution was optimal for the memory scores. Three clusters on each battery...
It has been shown that verbal working and associative memory have different developmental traject... more It has been shown that verbal working and associative memory have different developmental trajectories with working memory, taking a linear course from early childhood to adolescence, whereas associative memory takes a curvilinear course asymptoting at about age 12. This study made a determination of whether these trajectories tracked with 2 magnetic resonance spectroscopy imaging (MRSI) variables: phosphocreatine level (PCr) and gray matter percentage (GM%). In a cross-sectional study, 94 children ranging in age from 6-14 years were administered tests of verbal working and associative memory and underwent an MRSI procedure evaluating 6 major brain regions. The study considered PCr levels and GM% in the 6 regions. Loess curves were constructed plotting the memory tests and MRSI variables across age, and trajectories were evaluated. PCr showed a linear increase with age, particularly in the left superior temporal lobe with this increase closely tracking improvement in working memory ...
Intelligence tests are commonly administered to children following moderate-to-severe traumatic b... more Intelligence tests are commonly administered to children following moderate-to-severe traumatic brain injury (TBI). The Reynolds Intellectual Assessment Scales (RIAS) is a recently developed measure of intellectual ability that has a number of appealing features for assessing individuals with brain damage, but as yet has little validity information when applied to children with TBI or other forms of brain injury. It is therefore unclear whether RIAS scores are sensitive to brain injury and how they compare to older more well-established tests such as the Wechsler scales. The current article reports two studies that examine these matters in youth with TBI. The first study examined sensitivity of the RIAS to TBI in 110 children. Results indicated the TBI sample performed significantly worse compared with the standardization sample on all RIAS index scores. The second study included 102 children who were administered either the RIAS, Wechsler Intelligence Scale for Children-Third Editi...
Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2013
This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in... more This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in a sample of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) veterans referred for mild traumatic brain injury (mTBI). Three clusters were extracted, two of which were characterized by level of performance and the third with a unique performance pattern characterized by slow performance on the TMT B (Low B). Clusters did not differ on demographic or psychiatric variables. The Above Average cluster had better performance on measures of processing speed, working memory, and phonemic fluency compared with the Low B cluster. Results suggest that a subset of patients with mTBI perform poorly on TMT B, which subsequently predicts poorer cognitive functioning on several other neuropsychological measures. This subset may be vulnerable to cognitive changes in the context of mTBI and multiple comorbidities while a number of other patients remain cognitively unaf...
There is increasing evidence that schizophrenia (SZ) and bipolar disorder (BD) share a number of ... more There is increasing evidence that schizophrenia (SZ) and bipolar disorder (BD) share a number of cognitive, neurobiological, and genetic markers. Shared features may be most prevalent among SZ and BD with a history of psychosis. This study extended this literature by examining reinforcement learning (RL) performance in individuals with SZ (n = 29), BD with a history of psychosis (BD+; n = 24), BD without a history of psychosis (BD-; n = 23), and healthy controls (HC; n = 24). RL was assessed through a probabilistic stimulus selection task with acquisition and test phases. Computational modeling evaluated competing accounts of the data. Each participant's trial-by-trial decision-making behavior was fit to 3 computational models of RL: (a) a standard actor-critic model simulating pure basal ganglia-dependent learning, (b) a pure Q-learning model simulating action selection as a function of learned expected reward value, and (c) a hybrid model where an actor-critic is "augment...
Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2014
Low IQ has recently been shown to predict effort test failure in healthy and neurological populat... more Low IQ has recently been shown to predict effort test failure in healthy and neurological populations. Although low IQ is common in schizophrenia (SZ), its effect on effort test performance remains unclear. Participants included 60 outpatients with SZ and 30 demographically matched healthy controls (CN) who received a battery of neuropsychological tests. Insufficient effort was calculated using the Digit Span Age-Corrected Scaled Score Effort Index and the Finger Tapping Effort Index. A total of 33.3% SZ and 6.7% CN fell below the Digit Span Age-Corrected Scaled Score Effort Index cut-off χ(2)(1, 89) = 7.70, p < 0.01, and 35.7%SZ and 3.3% CN fell below the Finger Tapping Effort Index cut-off χ(2)(1, 85) = 11.10, p < 0.001. Low IQ is a significant predictor of falling below effort cut-off scores for indices embedded in standard neuropsychological tests. IQ may complicate the interpretation of effort testing in SZ patients who may have low motivation, but are not feigning cognit...
A comparison was made among participants with schizophrenia and those with structural lateralized... more A comparison was made among participants with schizophrenia and those with structural lateralized or diffuse brain damage in order to determine the extent to which the cognitive profile of the schizophrenia sample resembled the profiles obtained from patients with left-hemisphere, right-hemisphere, and diffuse brain damage. The Halstead-Reitan Neuropsychological Battery was used as the testing procedure. The data were subjected to discriminant analysis in order to obtain frequencies of predicted classification of the participants with schizophrenia into schizophrenia, left-hemisphere, right-hemisphere, and diffuse groups. Half of the participants with schizophrenia were classified into the schizophrenia group. The other half was evenly distributed across the left-hemisphere, right-hemisphere, and diffuse brain damage groups. There was not a disproportionately large number of participants classified into the left-hemisphere group. Comparisons among these four predicted groups were ac...
The authors' goal was to determine whether cognitively impaired patients with schizophrenia e... more The authors' goal was to determine whether cognitively impaired patients with schizophrenia exhibit age-related cognitive declines similar to those of patients with schizophrenia who do not have substantial cognitive impairment. Correlation coefficients were computed between age and the Average Impairment Rating, a summary index of cognitive ability, in a group of 77 patients with schizophrenia. These patients were clustered into two groups: one with near-normal cognitive function (N=51) and one with severely impaired cognitive function (N=26). A group of patients with senile dementia (N=21) and another comparison group of nonschizophrenic patients (N=299) were used as reference groups. There were significant correlations between age and the Average Impairment Rating in all groups except the cognitively impaired patients with schizophrenia, in which a zero-order correlation was obtained. Patients with schizophrenia who have substantial cognitive impairment do not have the signif...
Archives of clinical neuropsychology : the official journal of the National Academy of Neuropsychologists, 2013
This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in... more This study used cluster analysis to examine variability in Trail Making Test (TMT) performance in a sample of Operation Enduring Freedom/Operation Iraqi Freedom/Operation New Dawn (OEF/OIF/OND) veterans referred for mild traumatic brain injury (mTBI). Three clusters were extracted, two of which were characterized by level of performance and the third with a unique performance pattern characterized by slow performance on the TMT B (Low B). Clusters did not differ on demographic or psychiatric variables. The Above Average cluster had better performance on measures of processing speed, working memory, and phonemic fluency compared with the Low B cluster. Results suggest that a subset of patients with mTBI perform poorly on TMT B, which subsequently predicts poorer cognitive functioning on several other neuropsychological measures. This subset may be vulnerable to cognitive changes in the context of mTBI and multiple comorbidities while a number of other patients remain cognitively unaf...
Recent studies have examined heterogeneous neuropsychological outcomes in childhood traumatic bra... more Recent studies have examined heterogeneous neuropsychological outcomes in childhood traumatic brain injury (TBI) using cluster analysis. These studies have identified homogeneous subgroups based on tests of IQ, memory, and other cognitive abilities that show some degree of association with specific cognitive, emotional, and behavioral outcomes, and have demonstrated that the clusters derived for children with TBI are different from those observed in normal populations. However, the extent to which these subgroups are stable across abilities has not been examined, and this has significant implications for the generalizability and clinical utility of TBI clusters. The current study addressed this by comparing IQ and memory profiles of 137 children who sustained moderate-to-severe TBI. Cluster analysis of IQ and memory scores indicated that a four-cluster solution was optimal for the IQ scores and a five-cluster solution was optimal for the memory scores. Three clusters on each battery...
It has been shown that verbal working and associative memory have different developmental traject... more It has been shown that verbal working and associative memory have different developmental trajectories with working memory, taking a linear course from early childhood to adolescence, whereas associative memory takes a curvilinear course asymptoting at about age 12. This study made a determination of whether these trajectories tracked with 2 magnetic resonance spectroscopy imaging (MRSI) variables: phosphocreatine level (PCr) and gray matter percentage (GM%). In a cross-sectional study, 94 children ranging in age from 6-14 years were administered tests of verbal working and associative memory and underwent an MRSI procedure evaluating 6 major brain regions. The study considered PCr levels and GM% in the 6 regions. Loess curves were constructed plotting the memory tests and MRSI variables across age, and trajectories were evaluated. PCr showed a linear increase with age, particularly in the left superior temporal lobe with this increase closely tracking improvement in working memory ...
Intelligence tests are commonly administered to children following moderate-to-severe traumatic b... more Intelligence tests are commonly administered to children following moderate-to-severe traumatic brain injury (TBI). The Reynolds Intellectual Assessment Scales (RIAS) is a recently developed measure of intellectual ability that has a number of appealing features for assessing individuals with brain damage, but as yet has little validity information when applied to children with TBI or other forms of brain injury. It is therefore unclear whether RIAS scores are sensitive to brain injury and how they compare to older more well-established tests such as the Wechsler scales. The current article reports two studies that examine these matters in youth with TBI. The first study examined sensitivity of the RIAS to TBI in 110 children. Results indicated the TBI sample performed significantly worse compared with the standardization sample on all RIAS index scores. The second study included 102 children who were administered either the RIAS, Wechsler Intelligence Scale for Children-Third Editi...
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