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PubMed2004

Posterior fossa lesion volume and slowed information processing in multiple sclerosis.

The relationship between performance on information processing efficiency measures and MRI-derived lesion volume including global and regional T2 and T1 lesion volumes was investigated in 20 patients with relapsing-remitting multiple sclerosis (RRMS) and secondary progressive multiple sclerosis (SPMS). Processing speed, as measured by the Sternberg Memory Scanning Test, was significantly correlated with posterior fossa lesion volume and slowed reaction time in seven out of eight patients (six out of seven with SPMS) with any lesion volume in the posterior fossa suggesting a 'threshold effect'. Processing capacity as measured by the Salthouse Keeping Track Test was not significantly correlated with the MRI measures. Cognitive performance did not correlate with Expanded Disability Status Scale score, depression or fatigue, and patients performed within normal limits on tests of attention/concentration ability. The significant relationship between posterior fossa lesion volume and memory scanning speed in this study suggests that pathological damage in the posterior fossa may contribute to slowed cognitive processing and may be an important direction for future studies of cognitive function in multiple sclerosis. Lack of correlation of cognitive measures with the other MRI measures may be due to low lesion volume relative to other studies, sample composition, and limited pathological specificity of the MRI measures.

Adult↗

PubMed2006

Dissociation of the component processes of attention in healthy adults.

Cohen's [Cohen, R. (1993). The Neuropsychology of Attention. New York: Plenum Publishing] model of attention proposes four interrelated processes, namely Sensory Selective Attention, Response Selection/Control, Focus/Capacity, and Sustained Attention. Though this model has been supported in patient samples, it has not been examined in a healthy adult cohort. Using Principal Components Analysis, we examined the explanatory power of this model in 342 adults screened for significant medical and psychiatric history. The four derived components accounted for 58.7% of the total variance. Results were generally supportive of Cohen's [Cohen, R. (1993). The Neuropsychology of Attention. New York: Plenum Publishing] model, though further clarification of the relationship between processing speed and more complex aspects of attention (e.g. working memory, set shifting) is needed. These findings support the notion that attention is not a unitary process, but instead comprised of distinct components. Future studies including both neuropsychological testing and functional neuroimaging may provide important insight into the underpinnings of attentional processes.

Adolescent↗

PubMed2005

Executive functions and ADHD in adults: evidence for selective effects on ADHD symptom domains.

Dual-process models of attention-deficit/hyperactivity disorder (ADHD) suggest that both executive functioning and regulatory functions (e.g., processing speed) are involved and that executive function weaknesses may be associated specifically with symptoms of inattention-disorganization but not hyperactivity-impulsivity. Adults aged 18-37 (105 with ADHD, 90 controls) completed a neuropsychological battery. The ADHD group had weaker performance than did the control group (p<.01) on both executive and speed measures. Symptoms of inattention-disorganization were uniquely related to executive functioning with hyperactivity-impulsivity controlled. Inattention was associated with slower response speed, and hyperactivity-impulsivity with faster output speed. Results were not accounted for by IQ, age, gender, education level, or comorbid disorders. Findings are discussed in terms of developmental and dual-process models of ADHD leading into adulthood.

Adolescent↗

PubMedDate not supplied

Sentence comprehension in children with specific language impairment: effects of input rate and phonological working memory.

BACKGROUND: Many children with specific language impairment (SLI) exhibit sentence comprehension difficulties. In some instances, these difficulties appear to be related to poor linguistic knowledge and, in other instances, to inferior general processing abilities. Two processing deficiencies evidenced by these children include reduced linguistic processing speed and diminished phonological working memory (PWM) capacity. While providing children with SLI a slower input rate appears to facilitate their immediate (real-time) processing of language; it is not known whether such a manipulation might also promote better offline (conventional) sentence comprehension. Complicating the potential benefits of a slower input rate on these children's offline comprehension is that a slower input rate might negatively interact with their PWM deficit. That is, a slower presentation rate may have the unintended consequence of placing too great a temporal burden on these children's vulnerable PWM system, thereby leading to even poorer comprehension. That is, a slower input rate presumably requires the listener to store previously processed information for a longer period while new, incoming material is being processed. AIMS: To investigate the interaction of input rate and PWM capacity on the sentence comprehension of children with SLI. It was hypothesized that if a slower input rate negatively affects the PWM functioning of children with SLI, these children would comprehend significantly fewer sentences presented at a slower rate versus sentences presented at a normal rate. It was also hypothesized that input rate should have no differential effect on the typically developing control children. METHODS & PROCEDURES: A group of 12 school-age children with SLI, a group of 12 age-matched children (CA), and a group of 12 receptive syntax-matched (RS) children (all with normal-range non-verbal IQ and hearing) completed a conventional picture-pointing sentence comprehension task. Sentences were presented at a normal speaking rate and a slower rate (25% time expanded). Children also completed a non-word repetition task, which served as an index of PWM capacity. OUTCOMES & RESULTS: Results of the PWM task revealed that the children with SLI repeated fewer three- and four-syllable non-words than both the CA and RS children, suggesting they had reduced PWM capacity. On the sentence comprehension task, a significant group by input rate interaction emerged. The children with SLI yielded significantly poorer comprehension of normal-rate sentences compared with both the CA and RS children. Whereas input rate had no differential effect on CA and RS children's comprehension, the comprehension of the children with SLI improved to the level of RS children in the slow-rate condition. Correlational analyses showed no significant association between PWM and sentence comprehension in either rate condition for any of the groups. CONCLUSIONS: Together, these findings suggest that the simple manipulation of altering speaking rate to children with SLI indeed can facilitate sentence comprehension, with no apparent detrimental effect on the operations of their PWM system.

Child↗

PubMed2001

[Change in effects of motor preparation due to priming as a function of the amount of practice].

The goal of the present experiment is to assess the effects of motor preparation on reaction time (RT) as a function of practice. We used a priming procedure to induce different levels of motor preparation. In reaction to a visual signal, the 16 participants had to respond with a flexion or an extension of the right or left wrist. Each participant performed 6120 successful trials divided into 34 experimental series. The first analysis of RT as a function of the type of cue (valid, neutral, or invalid) suggested that the time needed (a) to inhibit the prepared response and (b) to program the required one, remains stable throughout practice. A second analysis on the amount of information to be processed according to type of cue (0.42, 2.00, and 3.58 bits) indicated that central processing speed did not vary with practice. Indeed, only RT for the 0 bit condition decreased during the first 720 trials, suggesting that only the peripheral processes were influenced in early learning.

Adult↗

PubMed2005

Poor premorbid social functioning and theory of mind deficit in schizophrenia: evidence of reduced context processing?

Investigations have demonstrated deficits in theory of mind (ToM) ability in schizophrenia. Yet, the development of, and mechanisms associated with these deficits are not well understood. The present investigation examined the hypothesis that, among chronic schizophrenia patients, impaired ToM is associated with failures in context processing, greater disorganized symptoms, and poor premorbid functioning. Forty-two inpatients with schizophrenia spectrum disorders were assessed on tests of ToM, visual and linguistic context processing, executive functioning, and verbal IQ. Symptomatology and premorbid functioning were also assessed. Results revealed that more impaired ToM was associated with poorer performance on both visual and linguistic context processing measures and higher ratings of disorganization on the BRRS. ToM was also associated with poorer childhood social functioning and an earlier age of illness onset. ToM was not associated with verbal processing speed, verbal fluency, response inhibition, sequence learning, or estimated verbal IQ. A significant regression model including measures of childhood peer problems and visual and language context processing significantly predicted ToM performance and accounted for 43% of the variance. These findings suggest that, among chronic schizophrenia patients, deficits in ToM ability may be the result of context processing impairments. These impairments may be a factor in both poor social functioning during childhood and greater disorganized symptoms after illness onset.

Adult↗

PubMed1982

Analysis and restitution of visual function in a case of cerebral amblyopia.

In a patient suffering from a severe bilateral dysfunction in both occipital and parietal areas we have found: (1) A loss of contrast-sensitivity, being strongest in the range of spatial frequencies where the normal eye is most sensitive; (2) Virtually normal grating resolution, a severe loss in letter acuity (about 15-fold), and a very strong loss in vernier acuity (about 100-fold); (3) Rapid partial recovery of contrast sensitivity due to stimulation; (4) Slow partial recovery of letter acuity due to CAM rotating grating treatment; (5) No improvement of a 10-fold temporal retardation in the speed of reading. Evidence is presented that the residual impairment of vision depends upon improper synthesis of spatial frequency components originating from a heavy loss in processing speed and abnormally long store duration for high spatial frequency information.

Adult↗

PubMed1989

Mental slowing in elderly persons: a cognitive psychophysiological analysis.

In recent attempts to formulate an integrative model of mental slowing in elderly persons, regression analyses have been done in which reaction-time data from a large number of studies spanning a broad range of speeded decision-making tasks were combined. The results of these meta-analyses were then used to support the conclusion that there is a generalized, proportional decline in mental processing speed among elderly adults that affects all elements of mentation equally. We present a series of similar regression analyses in which both reaction time and the latency of the P300 component of the event-related brain potential are included. The results of these analyses indicate that there are elements of mental processing that may be slowed additively, not proportionately, in older persons. Furthermore, the results raise some questions about the logic underlying the interpretation of the meta-regression analysis.

Adult↗

PubMed2005

Asymmetric interference between sex and emotion in face perception.

Previous research with speeded-response interference tasks modeled on the Garner paradigm has demonstrated that task-irrelevant variations in either emotional expression or facial speech do not interfere with identity judgments, but irrelevant variations in identity do interfere with expression and facial speech judgments. Sex, like identity, is a relatively invariant aspect of faces. Drawing on a recent model of face processing according to which invariant and changeable aspects of faces are represented in separate neurological systems, we predicted asymmetric interference between sex and emotion classification. The results of Experiment 1, in which the Garner paradigm was employed, confirmed this prediction: Emotion classifications were influenced by the sex of the faces, but sex classifications remained relatively unaffected by facial expression. A second experiment, in which the difficulty of the tasks was equated, corroborated these findings, indicating that differences in processing speed cannot account for the asymmetric relationship between facial emotion and sex processing. A third experiment revealed the same pattern of asymmetric interference through the use of a variant of the Simon paradigm. To the extent that Garner interference and Simon interference indicate interactions at perceptual and response-selection stages of processing, respectively, a challenge for face processing models is to show how the same asymmetric pattern of interference could occur at these different stages. The implications of these findings for the functional independence of the different components of face processing are discussed.

Adolescent↗

PubMed1996

Color, orientation and cytochrome oxidase reactivity in areas V1, V2 and V4 of macaque monkey visual cortex.

Color and orientation processing in the macaque monkey first segregates into cytochrome oxidase (CO)-rich blobs and -poor interblobs of area V1, from where the two streams flow through areas V2 and V4. This parallel representation is believed to enhance processing speed by compartmentalizing tasks of similar kinds, though our knowledge of the mechanisms is still elementary. We have examined the interaction and separation of color and orientation processing in neurons (n = 569) of the macaque visual cortex (V1, V2, V4) on the basis of microelectrode recordings. In all three areas, neurons selective for midspectral (MS) colors (e.g., yellow, green) were also found to be more orientation selective than those preferring endspectral (ES) colors (e.g., blue, red). The majority of achromatic (AC) cells responsive to bright stimuli were also orientation selective. When locations of cells and penetration columns were correlated with cytochrome oxidase (CO) landmarks in V1 and V2, V1 interblob and V2 interstripe cells were found to be predominantly midspectral and oriented, while V1 blob and V2 thin stripe cells were found to be predominantly endspectral and non-oriented. Cells preferring dark colors were found to cluster in thick stripes in V2, and in columns in V4. Separate clustering of midspectral (MS) and endspectral (ES) systems in V4 was also noted. With the results shown in a companion paper (Behav. Brain Res., 76 (1996) 51-70), the present data indicate that the visual system appears to optimize color and spatial acuity by separating chromatic information into non-oriented endspectral and oriented midspectral components.

Action Potentials↗

PubMed1992

ST analysis of Holter tapes.

In recent years, it has become increasingly clear that for an important subset of patients with coronary artery disease, many or all of their ischemic episodes are not accompanied by anginal pain. For these patients, it is desirable to detect these ischemic episodes as periods of ST-segment depression on Holter tapes. In the past, such detection has been difficult because the analysis methods were artifact-sensitive and failed to differentiate ischemic from nonischemic ST-segment changes. This work describes a new ST-segment analysis algorithm that has been added to the existing computer-based Holter analysis system. This system is highly artifact-resistant and has been designed to minimize the loss of processing speed while maintaining extremely high accuracy.

Algorithms↗

PubMedDate not supplied

[Neuropsychological evaluation in a case of multiple sclerosis].

INTRODUCTION: The neuropsychological assessment of patients with multiple sclerosis (MS) may be diagnostically useful to provide a patient's cognitive profile, to observe the spread of the deficit and to identify the peculiar areas that are more or less affected, in order to plan a long-term management and treatment. CLINICAL CASE: In this article, we present a case of cognitive dysfunction associated with a progressive MS in a 54 years woman, which was diagnosed six years ago. The magnetic resonance imaging showed demyelinating lesions at the periventricular region, with left predominance, and in the protuberance with signs of cortico-subcortical atrophy. We performed neuropsychological assessment of the main cognitive areas: orientation, attention, information processing, memory, general intelligence functioning, language, arithmetic, visual-spatial functioning, motor, executive functioning and personality. CONCLUSIONS: The results obtained point out serious alterations in the information speed processing, long term memory, motor, executive functioning and personality. This results go in a concordant way with the results reported in the consulted bibliography. Likewise, it is commented the resemblance of the cognitive deficit related to a pattern of subcortical dementia.

Affect↗

PubMed2001

Adult age differences in self-ordered pointing task performance: contributions from working memory, executive function and speed of information processing.

This study investigated adult age differences in, and predictors of, the performance of a test of executive function, the Self-Ordered Pointing Task (SOPT; Petrides & Milner, 1982). Performance on the SOPT is thought to rely on high level working memory processes, therefore, measures reflecting the common operationalization of working memory, along with measures of executive function and speed of information processing, were investigated as predictors of SOPT performance. Younger (aged 17-48 years) and older (aged 65-88 years) adults completed a 16-item, 3-trial, modified version of Shimamura and Jurica's (1994) version of the SOPT, and tests assessing working memory, executive function and speed. Results showed that younger adults made fewer errors on the SOPT. There was no age difference in the frequency of use of a clustering strategy. Contrary to expectations, working memory was not a good predictor of individual or age differences in SOPT performance. Instead, speed of processing, and to a lesser extent, measures of perseverations, made larger unique and overlapping contributions to the variance. The SOPT and its association, or dissociation, with other measures of working memory may be useful for research into the nature of working memory and executive function and the theoretical links between them.

Adolescent↗

PubMed1997

Attentional factors in response time variability after traumatic brain injury: an ERP study.

Reaction time (RT) is often used in the assessment of patients with traumatic brain injury (TBI), presumably because it reflects either information processing speed or attentional capacity. To clarify this distinction, we examined behavioral RT and the within-subject variability of RT as they relate to electrophysiological measures of attention and information processing. These include the P300 latency, which reflects stimulus evaluation time, P300 amplitude, which reflects attentional allocation, and the preresponse component of the contingent negative variation (CNV), which reflects sustained attention. We found that the latency and variability in behavioral RT were not correlated with the latency or variability of the P300, suggesting that stimulus evaluation time is not a major contributor to RT and its variability in this paradigm. However, among normal controls, RT was related to P300 amplitude, and therefore to attentional allocation. For the TBI subjects, it was the variability, not the speed, of RT that was related to P300 amplitude and to the preresponse component of the CNV. These data suggest that, while in normal controls RT reflects attentional allocation, among TBI subjects it is the variability in RT that is sensitive to the ability to allocate and sustain attention.

Adult↗

PubMed2006

Preliminary report: functional MRI of the brain may be the ideal tool for evaluating neuropsychologic and sleep complaints of patients with primary hyperparathyroidism.

BACKGROUND: The incidence, pattern, and severity of sleep disturbance and cognitive dysfunction has not been well characterized for patients with primary hyperparathyroidism (PHPT). There is no agreement on the mechanism of the development or resolution of such symptoms, and in no previous study has cerebral activity been functionally assessed and change documented following surgical cure of patients with PHPT. METHODS: We undertook a prospective analysis to obtain pilot data on 6 patients with PHPT. Functional magnetic resonance imaging (fMRI), formal neuropsychologic (NP) tests, and health-related quality of life (HRQL) measures that included sleep assessments were performed on patients before and after parathyroidectomy. Changes in cortical activation under both conflict and neutral conditions (distracting tasks) were recorded. RESULTS: Functional MRI demonstrated postoperative changes in medial prefrontal cortex activity during cognitive processing of conflict and nonconflict tasks. Further postoperative changes were noted in the dorsolateral prefrontal cortex and parietal cortex with shifts in activations. In addition to the fMRI findings, the patients demonstrated improvements in sleep and social behavior. They tended to experience less fatigue and their processing speed on cognitive tests improved. CONCLUSIONS: These data support the feasibility and willingness of patients with PHPT to undergo fMRI assessment. Preliminary findings reflected a generalized improvement in processing efficiency postoperatively compared with a patient's preoperative state, and the HRQL measures showed improved sleep. These findings mirror those expected with sleep dysfunction. Longitudinal assessment with advanced brain imaging technology, neuropsychological (NP), and sleep evaluations is warranted to further explore cognitive, sleep, and HRQL improvement after parathyroidectomy.

Adult↗

PubMed2003

N400 abnormalities in unmedicated patients with schizophrenia during a lexical decision task.

A lexical decision task was used to investigate semantic processing in schizophrenia. Eighteen unmedicated schizophrenics and 18 gender/age-matched controls were tested. Subjects were visually presented with pairs of words. The target word (S2) was either a non-word, semantically related, or unrelated to preceding word (S1). Subjects decided whether the S2 was a word or non-word. Event related potentials (ERPs) elicited by the S2, including N350, and the late positive component (LPC) were measured. The latency of the N350 was prolonged in schizophrenia. The N400 effect, measured by the mean amplitude (300-500 ms) from difference waves (unrelated word-related word, non-word-related word), was smaller in patients. Peak amplitude of the LPC was reduced and latency of the LPC was delayed in the schizophrenics. Behaviorally, control subjects responded much faster to related words compared to unrelated or non-words, while patients showed little difference in processing speed between word categories. A reduced N400 effect suggested inefficient utilization of the context, while prolonged latency of the ERP components suggested a general delay of semantic information processing in schizophrenia.

Adult↗

PubMed2001

Evaluation of cognitive performance in the heat by functional brain imaging and psychometric testing.

Military operations in tropical environments have imposed a significant challenge to the Australian Defence Forces (ADF). The hot and humid conditions are known to cause debilitating effects on soldiers deployed to northern regions of Australia, with the consequence that the effectiveness and efficiency of operations are severely compromised. While the adverse effects of thermal stress on soldiers' physiological capability are well established, this has not been confirmed for cognitive performance. A select range of psychometric tests were administered and functional brain electrical activity imaging was performed to investigate the impact of thermal stress on cognitive performance. The brain electrical activity of subjects was measured while undertaking a range of cognitive tasks. Steady State Probe Topography (SSPT), a novel brain imaging technology, was employed to monitor the changes in regional brain activity and neural processing speed of subjects under thermal stress. The psychometric test batteries included the following tasks; Rey Auditory Verbal Learning Test; Inspection Time; Digit Span test; a spatial working memory task; and the AX-continuous performance task. These tasks measure a range of cognitive processes including attention, memory, verbal learning, information processing and concentration. The functional brain imaging provided topographical information, which showed changes in electrical activity in response to thermal stress during cognitive performance. These changes in brain electrical activity and neural speed induced by thermal stress may help to identify the type of cognitive functions that are likely to be impaired under operational conditions. Results indicated that subjects experienced increasing cardiovascular strain through thermally neutral to thermally straining conditions. The results from the psychometric test battery showed some promising effects given the small sample size including deficits in working memory, in information retention and in information processing. There was also marked differences in the electrical responses of the brain when subjects were thermally strained. The Steady-State Visual Evoked Potential recordings showed an increase in amplitude and a decrease in latency, suggesting an increase in the utilisation of neural resources or effort by subjects to maintain the same level of performance as under thermally neutral conditions. The data are suggestive of the high sensitivity of brain imaging techniques with high temporal resolution to identify important decrements in cognitive performance in hostile environments.

Adult↗

PubMed2006

Effects of age and mild cognitive impairment on direct and indirect access to arithmetic knowledge.

The present study aimed at investigating age-related changes and mild cognitive impairment (MCI) related effects in simple arithmetic. To pursue this goal, MCI patients, healthy old adults and young adults performed three computerised tasks. The production (e.g., 3 x 4=?) and the verification task (3 x 4 12?) evaluated direct access to multiplication knowledge, the number-matching task (3 x 4 34?, 'do 3 x 4 and 34 have the same digits?') tested indirect access. In verification and number-matching, interference from related distractors (e.g., 3 x 4 followed by 16) relative to unrelated distractors (17) reflects access to stored fact representations as well as efficiency of inhibition processes. Results indicated that, compared to young adults, MCI and healthy old adults were slower in responding across tasks. In production and verification, analyses of individual latency regression slopes and intercepts suggested that these age effects were related to differences at peripheral processing stages (e.g., encoding) rather than at the central (arithmetic retrieval) stage. Differences between MCI and healthy elderly emerged only in the number-matching task. While in verification effects were comparable between groups, in number-matching MCI patients were more susceptible to interference from irrelevant information than healthy old participants. Overall, the present findings indicate that aging has a general effect on peripheral processing speed, but not on arithmetic memory retrieval. Parietal cortico-subcortical circuits mediating arithmetic fact retrieval (Dehaene, S., & Cohen, L. (1995). Towards an anatomical and functional model of number processing. Mathematical Cognition, 1, 83-120; Dehaene, S., & Cohen, L. (1997). Cerebral pathways for calculation: Double dissociation between rote verbal and quantitative knowledge of arithmetic. Cortex, 33, 219-250) thus seem to be preserved in normal aging and MCI. In contrast, MCI patients show enhanced interference in number-matching. This task-specific lack of inhibition may point to dysfunctional frontal cortico-subcortical networks in MCI.

Adult↗