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PubMed1994

Cognitive disorders and negative symptoms as correlates of motivational deficits in psychotic patients.

The problem of a possible lack of motivation to perform cognitive tasks, which is often encountered in psychotic patients, has been approached from the perspective of the 'energetics' of cognition (Hockey et al. 1986) and from the broader clinical context of psychosis as an 'amotivational syndrome' and its related negative symptoms. The presence of motivational deficits was investigated in a group of psychotic in-patients (N = 73, and 40 had schizophrenia) compared with a control group of non-psychotic psychiatric in-patients (N = 23). The motivational deficit was operationalized in terms of Sanders's (1983) cognitive-energetic model as a large effect of 'time-on-task' during a simple, monotonous reaction test. Significantly more psychotic patients than control patients showed evidence of this type of motivational deficit. The deficit appeared to be related with negative but not with positive symptoms of psychosis. Furthermore, the deficit was shown to be related to the cognitive disorders of psychosis, which have been amply documented in the literature, i.e. disorders of vigilance, verbal memory and distractibility. These results suggest that the cognitive disorders of psychosis are not of a 'computational' but of an 'energetical', i.e. motivational nature.

Adolescent↗
PubMed1994

Memory functions, alprazolam and exposure therapy: a controlled longitudinal study of agoraphobia with panic disorder.

Benzodiazepines (BZs) produce transient anterograde amnesia when given to normal subjects. The present longitudinal study assessed whether BZs impair memory functions in a clinically anxious group. Eighty-two agoraphobics with panic disorder were randomly allocated to one of four treatment groups resulting from a combination of two drug treatments (alprazolam or placebo) and two psychological treatments (exposure or relaxation). Of these, 38 subjects were assessed on a range of objective and subjective indices of memory and mood at three time points: before treatment, after 8 weeks of treatment and again at 24 weeks when patients had been free of medication from 5-8 weeks. Alprazolam produced pronounced impairments on a word recall task. At the 24-week medication-free follow-up, alprazolam patients were still impaired on the task compared with placebo patients. Alprazolam did not impair performance on an implicit memory task and did not affect digit span. Differences between psychological treatments emerged mainly in subjective memory effects. Findings are discussed in terms of the specificity of BZ-induced amnesia and differential tolerance to the varying effects of BZs. Implications are drawn out for the patient's ability to function optimally in daily life while taking alprazolam.

Adult↗
PubMed1998

Capacity limitations in short-term memory in schizophrenia: tests of competing hypotheses.

BACKGROUND: Capacity limitation theories have proved to be surprisingly resilient in characterizing some of the cognitive deficits in schizophrenia. However, this perspective has not generally been applied to short-term verbal memory tasks. We explored this issue by first attempting to ascertain if gross misallocations of processing resources might explain impairments in short-term memory in schizophrenia on a classic digit span task and in a second study by attempting to determine what effects delay and memory set size had on a divided attention short-term verbal memory paradigm. METHODS: In the first study 16 patients with schizophrenia and 21 normal controls received 40 trials of a three digit task and 20 trials of a six digit span task. As the absolute number of digits presented and duration of presentation in two conditions were identical, subjects thus had equivalent 'opportunities' to make errors if distraction, in the sense of misallocation of cognitive resources, were at the root of poor performance. In the second study 15 patients with schizophrenia and 15 normal controls were tested in conditions in which two, four or six words were presented and in which rehearsal was prevented by an interference task (colour naming) for delays of 5, 10 or 15 s. RESULTS: Patients had disproportionate difficulty on the six digit rather than the three digit condition, suggesting that deficits in the verbal working memory short-term store may not be the result of attentional factors. In the second study, patients' performance was differentially worsened by the interference task, by memory set size (i.e. a capacity limitation) and by delay, a measure of decay rate. CONCLUSIONS: In concert, these studies demonstrate that schizophrenia patients have difficulties on verbal short-term memory span tasks not because of misallocation of resources, but rather because of limitations in 'representational capacity' and maintenance of information over delays.

Adult↗
PubMed1996

Comparative study of visual and verbal short-term memory in English and Spanish speakers: testing a linguistic hypothesis.

It has been proposed that differences in digit span performance between English and Spanish speakers are due to the greater number of syllables per digit in the Spanish language. To test this hypothesis, we studied the performance of 30 English- and 30 Spanish-speaking elders on the Wechsler Adult Intelligence Scale-Revised (WAIS-R) Digit Span Subtest, a modified digit span test that was linguistically comparable for both languages, and the Corsi Block Test. Consistent with previous reports, we found that English speakers scored significantly higher than Spanish speakers on WAIS-R Digit Span Forward. Group differences were reduced on the modified Digit Span Forward, but remained significant. English and Spanish speakers scored comparably on Digit Span Backward (WAIS-R and modified) and Visual Span. We suggest that although differences in the number of syllables per digit string are in part responsible for the lower performance of Spanish speakers on Digit Span Forward, cultural and educational issues also contribute to the observed differences between English and Spanish speakers.

Adult↗
PubMed2006

Working memory deficits in multiple sclerosis: comparison between the n-back task and the Paced Auditory Serial Addition Test.

Working memory (WM) deficits are common in multiple sclerosis (MS). The Paced Auditory Serial Addition Test (PASAT) is used frequently to measure WM in clinical settings. The n-back paradigm is used often in experimental studies of WM. One unique component of the n-back task is that it provides a measure of reaction time (RT), an additional behavioral index of processing speed and task difficulty. Despite the use of both tasks to measure WM, their common variance has not been documented. We tested 32 MS patients and 20 controls; performance measures were obtained for both tasks. Compared with controls, MS patients generally had poorer performance on both the PASAT and n-back task. MS patients also had slower RTs on the n-back than controls and showed more slowing than controls as a function of WM load. Correlational analyses showed a high correspondence between performance measures on the PASAT and n-back. Principal components analysis pointed to a common feature of the PASAT, n-back, and specific other neuropsychological measures, that is, processing speed. Although the PASAT and n-back were shown to have a significant amount of shared variance, each test has specific advantages and disadvantages for use in clinical populations.

Acoustic Stimulation↗
PubMed2001

Movement preparation in high-functioning autism and Asperger disorder: a serial choice reaction time task involving motor reprogramming.

Autism and Asperger disorder have long been associated with movement abnormalities, although the neurobehavioural details of these abnormalities remain poorly defined. Clumsiness has traditionally been associated with Asperger disorder but not autism, although this is controversial. Others have suggested that both groups demonstrate a similar global motor delay. In this study we aimed to determine whether movement preparation or movement execution was atypical in these disorders and to describe any differences between autism and Asperger disorder. A simple motor reprogramming task was employed. The results indicated that individuals with autism and Asperger disorder have atypical movement preparation with an intact ability to execute movement. An atypical deficit in motor preparation was found in Asperger disorder, whereas movement preparation was characterized by a "lack of anticipation" in autism. The differences in movement preparation profiles in these disorders were suggested to reflect differential involvement of the fronto-striatal region, in particular the supplementary motor area and anterior cingulate.

Adolescent↗
PubMed2003

Long-term memory in high-functioning autism: controversy on episodic memory in autism reconsidered.

Two studies were conducted to examine the nature of verbal long-term memory (LTM) in people with autism. In Study 1, undergraduate students showed better LTM and more verbal associations for concrete than abstract nouns. Probability of recall of the nouns strongly correlated with the number of associations with those nouns. In Study 2, unlike controls, autistic subjects did not show superior recall of concrete over abstract nouns despite overall comparable performance. A highly significant correlation between probability of recall and associative value was found only in the controls. Furthermore, there was an unusual correlation between LTM performance and a nonverbal measure in the autistic group. The results were discussed in terms of the relation between episodic memory and semantic memory.

Adolescent↗
PubMed2004

Sequential rearrangements of the ensemble activity of putamen neurons in the monkey brain as a correlate of continuous behavior.

Simultaneous recordings were made of the spike activity of groups of 6-7 neurons in the putamen in two monkeys (Macaca nemestrina and Macaca mulatta) during performance of alternative spatial selection. Discriminant analysis was used to evaluate the magnitude of rearrangements in spike activity in groups of neurons during transitions from each step of the behavioral program to the next, along with the degree of differences in reactivity mosaics formed at each step in different versions of task execution. Rearrangements in spike activity were noted at all steps of the program. The dynamics of rearrangements on selection of the right and left feeders were different, leading to the appearance of significant differences in the reactivity mosaics at the decision-taking and reinforcement-receiving steps. The rearrangements preceding voluntary movement of one hand were more marked in the contralateral hemisphere. During performance of movements, the volume of rearrangements could increase, though differences in rearrangements accompanying movements of the right and left hands decreased. On receipt of reinforcement, rearrangements were greater when the animals selected a specified feeder (the left feeder) independently of which hemisphere was recorded.

Action Potentials↗
PubMed2003

Alpha-adrenoceptor-mediated modulation of 5-HT2 receptor agonist induced impulsive responding in a 5-choice serial reaction time task.

The activation of 5-HT2A receptors has been shown to enhance the probability of premature responding, regarded as a form of motor impulsive behaviour. At the behavioural level, the interaction of alpha-adrenoceptors and 5-HT2 receptors has been linked to head twitch behaviour, regarded as an experimental model of compulsive behaviour. The aim was to determine whether the probability of premature responding induced by an excess activation of 5-HT2A receptors can be modulated by the blockade of alpha1- or alpha2- adrenoceptors. In the experiments, the 5-choice serial reaction time task was used to measure attention and response control of the rats. The experiments assessed the effects of (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI) 0.1-0.2 mg/kg subcutaneously, a 5-HT2A/2C agonist, and prazosin, an alpha1-adrenoceptor antagonist, alone or in combination, on the performance of rats. In an additional experiment to examine the possible role of the alpha2-adrenoceptors, a potent, selective and specific alpha2-adrenoceptor antagonist, atipamezole, was given alone or in combination with DOI. Results showed that DOI increased the probability of premature responses, but it did not affect the choice accuracy. Prazosin (0.1 or 0.3 mg/kg, subcutaneously), given on its own had no effects on probability of responding prematurely, but prazosin (0.3 mg/kg.) was able to attenuate the DOI-induced responding. Atipamezole (0.1 mg/kg, s.c.) did not attenuate the effect of DOI on probability of premature responding. When given at lower doses, DOI (0.03 mg/kg) and atipamezole (0.03 mg/kg) synergistically increased the probability of premature responding, whereas a higher dose of atipamezole (0.3 mg/kg) on its own increased the probability of responding prematurely, but this effect was not additive to that of 0.1 mg/kg DOI. These data indicate that 5-HT2 receptor activation enhances impulsive responding and this effect can be diminished by the blockade of alpha1-adrenoceptors. Atipamezole, an alpha2-antagonist, enhances the probability of premature responding and shares the mechanism of action with the 5-HT2 agonist in this respect. These results provide evidence for an interaction between the serotonergic 5-HT2 receptors and alpha-adrenoceptors in the modulation of response control to the motor impulsivity type of behaviour (premature responding) in addition to that of compulsory behaviour (head shakes) found previously.

Adrenergic alpha-Antagonists↗
PubMed1997

Changing relations between phonological processing abilities and word-level reading as children develop from beginning to skilled readers: a 5-year longitudinal study.

Relations between phonological processing abilities and word-level reading skills were examined in a longitudinal correlational study of 216 children. Phonological processing abilities, word-level reading skills, and vocabulary were assessed annually from kindergarten through 4th grade, as the children developed from beginning to skilled readers. Individual differences in phonological awareness were related to subsequent individual differences in word-level reading for every time period examined. Individual differences in serial naming and vocabulary were related to subsequent individual differences in word-level reading initially, but these relations faded with development. Individual differences in letter-name knowledge were related to subsequent individual differences in phonological awareness and serial naming, but there were no relations between individual differences in word-level reading and any subsequent phonological processing ability.

Aptitude↗
PubMed1999

What develops in working memory? A life span perspective.

This study investigated whether working-memory (WM) span differences across age are attributable to specific or general processing functions. The study compared 9 age groups (6, 8, 10, 13, 16, 24, 35, 45, 57 years) on verbal and visuospatial WM performance under initial (no probes or cues), gain (cues that bring performance to an asymptotic level), and maintenance conditions (asymptotic conditions without cues). (a) Age-related performance differences in WM were found across all conditions and were not isolated to specific processes, (b) significant performance differences remained among age groups on gain and maintenance conditions, and (c) the gain (accessing new information) and maintenance conditions (maintenance of old information) for verbal and visuospatial WM tasks contributed independent variance to age-related performance. The results support a general capacity explanation of age-related differences. These differences in capacity reflect demands placed on both the accessing of new information and the maintenance of old information.

Achievement↗
PubMed1996

Reduced top-down influence in auditory perceptual organization in schizophrenia.

Perceptual organization of auditory information is influenced by both the physical characteristics and the categorization of irrelevant information. This study sought to determine the degree to which schizophrenia patients could utilize acoustic properties and contextual cues (top-down factors) to segregate relevant from irrelevant material in an auditory stream. On a modification of I. Neath, A. M. Surprenant, and R. G. Crowder's (1993) auditory suffix task, both schizophrenia and control participants demonstrated better recall of relevant information when irrelevant information had different physical characteristics, compared with when both arose from the same source. In contrast, schizophrenia patients were unaffected by a contextual manipulation that allowed controls to reduce the interfering effect of an irrelevant stimulus. These data suggest that a reduced ability to utilize contextual information plays a role in the perceptual organization dysfunction in schizophrenia.

Adult↗
PubMed1997

Impaired precision, but normal retention, of auditory sensory ("echoic") memory information in schizophrenia.

Working memory is the type of memory that allows one to hold information in mind while working on a task or problem. The present study investigated attention-independent auditory sensory ("echoic") memory in 18 schizophrenic participants and 17 controls. Schizophrenic participants showed impaired delayed tone matching performance in comparison with controls. However, when groups were matched for performance at 1 s by varying the difficulty of the task across groups, schizophrenic participants showed normal retention of information as reflected in normal tone matching performance. These findings demonstrate that schizophrenic may be in the sensitivity of the system rather than the duration for which memory traces were retained.

Adult↗