Biomedical subjects

Robin G Morris

Publications and source records attributed to Robin G Morris.

18 recordsLinked to original sources

PubMed2006

Hippocampal volume and cognitive function in anorexia nervosa.

We hypothesised that hippocampal volume would be reduced in underweight anorexia nervosa (AN) and associated with impaired hippocampus-dependent cognitive function. Hippocampal and whole brain volumes were measured in 16 women with AN and 16 matched healthy women using magnetic resonance imaging (MRI) and a manual tracing method. Participants also completed the Doors and People Test of hippocampus-dependent memory and an IQ test. After adjustment for total cerebral volume, there was significant bilateral reduction in hippocampal volume in the AN group (8.2% right; 7.5% left). There was no evidence of impaired hippocampus-dependent cognitive function and no evidence of a relationship between hippocampal volume and clinical features of AN. The reduced hippocampal volume in anorexia nervosa is not associated with changes in cognitive function. To understand the cause and consequence of hippocampal size and function, it will be important to integrate endocrine, neuropsychological and neuroimaging studies.

Adolescent↗

PubMed2005

Social cognition in frontal lobe epilepsy.

This study investigated the social cognitive functioning of patients with frontal lobe epilepsy (FLE), using a range of procedures that have shown impairments in patients following focal prefrontal brain lesions. Fourteen participants with FLE were compared with 14 healthy controls on story tests of theory of mind (ToM), faux pas appreciation, mental and physical state cartoon humor appreciation, facial emotional recognition, and the ability to perceive eye gaze expression. They were not impaired on story tests of ToM and showed only a trend toward impairment on a test of faux pas appreciation. They were impaired on humor appreciation, with both mental and physical state cartoons, and on their recognition of facial emotion and perception of eye gaze expression. Hence the patients with FLE exhibited impairments on tests of social cognition following a distinct pattern, with relatively preserved ToM, but impaired humor appreciation and ability to detect emotional expression.

Adult↗

PubMed2005

Cognitive performance in presumed obligate carriers for psychosis.

We report cognitive performance of a group of individuals who are likely to have transmitted liability to psychosis to their offspring. Out of 230 relatives of patients with psychosis, 27 met our criteria for a presumed obligate carrier, that is a non-psychotic individual who had a parent or a sibling as well as an offspring with psychosis. The presumed obligate carriers showed impairments in verbal memory and in visuospatial manipulations, suggesting that these individuals transmit vulnerability for psychosis to their offspring in terms of a disability to recall verbal information and an impaired capacity to perceive spatial relations.

Cognition Disorders↗

PubMed2004

Allocentric spatial memory in humans with hippocampal lesions.

An immersive virtual reality (IVR) system was used to investigate allocentric spatial memory in a patient (PR) who had selective hippocampal damage, and also in patients who had undergone unilateral temporal lobectomies (17 right TL and 19 left TL), their performance compared against normal control groups. A human analogue of the Olton [Olton (1979). Hippocampus, space, and memory. Behavioural Brain Science, 2, 315] spatial maze was developed, consisting of a virtual room, a central virtual circular table and an array of radially arranged up-turned 'shells.' The participant had to search these shells in turn in order to find a blue 'cube' that would then 'move' to another location and so on, until all the shells had been target locations. Within-search errors could be made when the participants returned to a previously visited location during a search, and between-search errors when they revisited previously successful, but now incorrect locations. PR made significantly more between-search errors than his control group, but showed no increase in within-search errors. The right TL group showed a similar pattern of impairment, but the left TL group showed no impairment. This finding implicates the right hippocampal formation in spatial memory functioning in a scenario in which the visual environment was controlled so as to eliminate extraneous visual cues.

Adult↗

PubMed2004

The relationship between volumetric brain changes and cognitive function: a family study on schizophrenia.

BACKGROUND: We examined the cerebral correlates of intelligence, memory, and executive processing in 56 patients with schizophrenia or schizoaffective disorder and 90 of their nonpsychotic relatives to establish whether the pattern of structure--function relationships in these two groups was different from that in 55 control subjects. METHODS: Magnetic resonance imaging data were acquired, and volumetric measurements were made for whole brain, prefrontal region, lateral ventricles, third ventricle, temporal lobes, hippocampi, and cerebellum. RESULTS: In the total sample, full intelligence quotient (IQ) and verbal IQ correlated with the volume of the whole brain and right hippocampus; the latter was also associated with performance IQ. Left hippocampal size was associated with verbal IQ and, in control subjects and nonpsychotic relatives only, with estimated full IQ. Delayed verbal memory was linked to cerebellar and inversely to left hippocampal volume. Discrepancies in the relationship pattern emerged in patients with schizophrenia between left hippocampus and measures of IQ and verbal memory. CONCLUSIONS: The latter data indicate a loss of a normal structure--function relationship in schizophrenia and might reflect a functional compensation occurring secondary to early neurodevelopmental impairment.

Adolescent↗

PubMed2004

Material-specific recognition memory deficits elicited by unilateral hippocampal electrical stimulation.

Although the medial temporal lobe is thought to be critical for recognition memory (RM), the specific role of the hippocampus in RM remains uncertain. We investigated the effects of transient unilateral hippocampal electrical stimulation (ES), subthreshold for afterdischarge, on delayed item RM in epilepsy patients implanted with bilateral hippocampal depth electrodes. RM was assessed using a novel computer-controlled test paradigm in which ES to left or right hippocampus was either absent (baseline) or synchronized with item presentation. Subsequent yes-no RM performance revealed a double dissociation between material-specific RM and the lateralization of ES. Left hippocampal ES produced word RM deficits, whereas right hippocampal ES produced face RM deficits. Our findings provide the first demonstration in humans that selective unilateral stimulation-induced hippocampal disruption is sufficient to produce impairments on delayed RM tasks and provide support for the material-specific laterality of hippocampal function with respect to RM.

Adult↗

PubMed2004

A neuropsychological investigation of male premutation carriers of fragile X syndrome.

It is currently thought that fragile X syndrome (FraX; the most common inherited form of learning disability) results from having more than 200 cytosine-guanine-guanine (CGG) trinucleotide repeats, with consequent methylation of the fragile X mental retardation (FMR1) gene and loss of FMR1 protein (FMRP). It was also considered that premutation carriers (with 55-200 CGG repeats) are unaffected, although a tremor/ataxia syndrome has recently been described in older adult male carriers. We reported that premutation expansion of CGG trinucleotide repeats affects brain anatomy, which, together with other studies, indicates that the molecular model for FraX needs modification. However, there are few studies on the cognitive ability of adult male premutation carriers. Thus, we selected 20 male premutation carriers on the basis of their genetic phenotype, and compared them to 20 male controls matched on age, IQ and handedness. We investigated intellectual functioning, executive function, memory, attention, visual and spatial perception, and language and pragmatics. The premutation carriers had significant impairments on tests of executive function (Verbal Fluency, Trail Making Test and Tower of London) and memory (Names sub-test of the Doors and People, Verbal Paired Associates Immediate Recall and Visual Paired Associates Delayed Recall sub-tests of the WMS-R, and Category Fluency Test for natural kinds). We therefore suggest that CGG trinucleotide repeats in the premutation range affect specific neuronal circuits that are concordant with specific neuropsychological deficits; and that these deficits reflect an emerging neuropsychological phenotype of premutation FraX.

Adult↗

PubMed2004

Cognitive flexibility in anorexia nervosa and bulimia nervosa.

The aim of this study was to determine if there are differences in cognitive flexibility in anorexia nervosa and bulimia nervosa. Fifty-three patients with an eating disorder (34 with anorexia nervosa and 19 with bulimia nervosa) and 35 healthy controls participated in the study. A battery of neuropsychological tests for cognitive flexibility was used, including Trail Making B, the Brixton Test, Verbal Fluency, the Haptic Illusion Test, a cognitive shifting task (CatBat) and a picture set test. Using exploratory factor analysis, four factors were obtained: 1: Simple Alternation; 2: Mental Flexibility; 3: Perseveration; and 4: Perceptual Shift. Patients with anorexia nervosa had abnormal scores on Factors 1 and 4. Patients with bulimia nervosa showed a different pattern, with significant impairments in Factors 2 and 4. These findings suggest that differential neuropsychological disturbance in the domain of mental flexibility/rigidity may underlie the spectrum of eating disorders.

Adult↗

PubMed2004

Long-term spatial memory: introduction and guide to the special section.

This article provides an introduction to the Special Section on Long-Term Spatial Memory in the journal Neuropsychology. It defines long-term spatial memory, explores how it has been considered historically, and provides brief descriptions of the principle cognitive mechanisms, with a guide to the terminology used in this field.

Animals↗

PubMed2004

Allocentric spatial memory activation of the hippocampal formation measured with fMRI.

Hippocampal activation was investigated, comparing allocentric and egocentric spatial memory. Healthy participants were immersed in a virtual reality circular arena, with pattern-rendered walls. In a viewpoint-independent task, they moved toward a pole, which was then removed. They were relocated to another position and had to move to the prior location of the pole. For viewpoint-dependent memory, the participants were not moved to a new starting point, but the patterns were rotated to prevent them from indicating the final position. Hippocampal and parahippocampal activation were found in the viewpoint-independent memory encoding phase. Viewpoint-dependent memory did not result in such activation. These results suggest differential activation of the hippocampal formation during allocentric encoding, in partial support of the spatial mapping hypothesis as applied to humans.

Adult↗

PubMed2004

Allocentric versus egocentric spatial memory after unilateral temporal lobectomy in humans.

Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories.

Adult↗

PubMed2003

The Maudsley Early-Onset Schizophrenia Study: cognitive function in adolescent-onset schizophrenia.

The neuropsychological correlates of adolescent-onset schizophrenia have been investigated very little to date. We assessed intelligence, memory and executive function in 42 patients with adolescent-onset schizophrenia and 43 healthy control subjects. Cases showed impairments in most cognitive variables. Despite the overall similarity with the quantitative and qualitative performance characteristics of later-onset patients in the literature, their cognitive profile displayed a unique feature: modification of the usual pattern of thinking latencies in the Tower of London Task. After adjusting for potential confounders, no effect of illness duration, symptoms or medication dose on patient performance emerged. However, longer exposure to medication predicted a lower level of performance in aspects of attention, psychomotor processing speed and spatial working memory. Our data are not consistent with worse cognition or progression of neuropsychological impairment in adolescent-onset schizophrenia.

Adolescent↗

PubMed2003

The Maudsley early onset schizophrenia study: cognitive function in adolescents with recent onset schizophrenia.

Neuropsychological function has been little studied early in the course of adolescent onset schizophrenia. The present study investigated cognitive function in adolescents with recent onset schizophrenia (n=20) and healthy controls (n=21), employing a comprehensive battery of intelligence, memory and executive function paradigms. Relative to the control group, the patients showed significant or near-significant deficits in more than half of the cognitive variables we examined. A substantial proportion of this broadly based neuropsychological deficit could be accounted for, at least in part, by a mild decrement in general intellectual ability. However, deficits in general and verbal memory remained highly significant after co-varying for IQ.

Adolescent↗

PubMed2003

Selectivity of verbal memory deficit in schizophrenic patients and their relatives.

Some of the relatives of people with schizophrenia show impairments of memory and executive function. It is not known, however, whether within these domains there is a class of processes that is especially impaired. Seventy schizophrenic or schizoaffective patients, 115 of their relatives and 66 normal controls underwent a series of assessments evaluating modality specific recall/learning, and aspects of executive functioning, including, planning ability, spatial working memory, strategy formation and rapid mental flexibility. The pattern of performance across cognitive processes was assessed using z-scores that allow direct comparison between tests with different raw score metrics. Selectivity of deficit was evaluated by subtracting the z-score of each cognitive process from the mean of the z-scores of those remaining. Patients performed out worse than controls on most measures, with verbal immediate recall and visual memory/learning the most impaired. Their relatives showed lower scores than controls on verbal and visual memory/learning and strategy formation; verbal memory and strategy formation remained impaired after eliminating those relatives with a psychiatric diagnosis. Consistent with the findings in their schizophrenic kin, healthy relatives also showed disproportionate impairments in verbal immediate recall. Our finding of a selective deficit in verbal memory among relatives suggests that such impairment constitutes a familial, probably genetic, risk factor for schizophrenia.

Adolescent↗

PubMed2003

Nonsyndromic mental retardation and cryptogenic epilepsy in women with doublecortin gene mutations.

DCX mutations cause mental retardation in male subjects with lissencephalypachygyria and in female subjects with subcortical band heterotopia (SBH). We observed four families in which carrier women had normal brain magnetic resonance imaging (MRI) and mild mental retardation, with or without epilepsy. Affected male subjects had SBH or pachygyria-SBH. In two families, the phenotype was mild in both genders. In the first family, we found a tyr138his mutation that is predicted to result in abnormal folding in the small hinge region. In the second family, we found an arg178cys mutation at the initial portion of R2, in the putative beta-sheet structure. Carrier female subjects with normal MRI showed no somatic mosaicism or altered X-inactivation in lymphocytes, suggesting a correlation between mild mutations and phenotypes. In the two other families, with severely affected boys, we found arg76ser and arg56gly mutations within the R1 region that are predicted to affect DCX folding, severely modifying its activity. Both carrier mothers showed skewed X-inactivation, possibly explaining their mild phenotypes. Missense DCX mutations may manifest as non-syndromic mental retardation with cryptogenic epilepsy in female subjects and SBH in boys. Mutation analysis in mothers of affected children is mandatory, even when brain MRI is normal.

Adolescent↗

PubMed2003

Pre- and postoperative intracarotid amytal procedure: an assessment of validity.

The intracarotid amytal procedure (IAP) was used twice to assess the suitability of three male patients for two successive neurosurgical procedures to relieve intractable temporal lobe epilepsy. First an amygdalohippocampectomy was performed, then further tissue was removed in a temporal lobe resection because their seizures had failed to remit. Repetition of the IAP following amygdalohippocampectomy when there was a known excision allowed inferences to be made regarding its validity in assessing lateralization of language functioning, memory functioning, and lateralization of seizure focus. The procedure was found to be reliable in assessing both language dominance and adequacy of memory functioning of the hemisphere contralateral to the lesion site. The procedure's third function of lesion lateralization was valid for identifying the known neurosurgical lesion. However, it was less successful in corroborating the lateralization of seizure focus before amygdalohippocampectomy. Differences in cognitive outcome between the two neurosurgical procedures are discussed.

Adult↗

PubMed2003

Lateralising value of neuropsychological protocols for presurgical assessment of temporal lobe epilepsy.

PURPOSE: To estimate the value of neuropsychological measurements in determining the side of seizure onset for presurgical assessment in patients with temporal lobe epilepsy. The lateralising value of neuropsychological protocols was evaluated for all patients and in subpopulations depending on surgical outcome with regard to seizure control, speech dominance, neuropathology, and need for intracranial EEG recordings. METHODS: A battery of neuropsychological procedures was carried out preoperatively in 125 patients who underwent left (n = 66) or right (n = 59) temporal lobectomies. Binary logistic regression analysis was performed to find sets of variables that allowed the best prediction of the side of seizure onset (assumed to be the operated-on side). RESULTS: Combinations of noninvasive neuropsychological tests and Wada subscores showed the highest lateralising values: 80.8% for all patients, 79.4% in seizure-free patients, 86.0% in patients not rendered seizure free, 85.7% in left speech patients, 77.8% in non-left speech patients, 89.3% in patients with mesial temporal sclerosis (MTS), 78.1% in non-MTS patients, 80.3% in patients who underwent intracranial EEG recordings, and 77.3% in those who did not. CONCLUSIONS: The lateralising value (80-90%) of neuropsychological protocols appears similar to that of other tests widely accepted for lateralisation (ictal and interictal scalp EEG and neuroimaging). Attention should be paid to neuropsychological results, particularly from the Wada test, during presurgical assessment of temporal lobe epilepsy, as they can provide strong support for findings from other lateralising tests, particularly in patients with presumed MTS or in left-speech patients.

Adult↗

PubMed1990

Relations between source amnesia and frontal lobe functioning in older adults.

A study is reported in which the relations among normal aging, source amnesia, and frontal lobe functioning were explored. Twenty-four older adults (aged 60-84 years) were tested on their ability to remember where they had acquired new factual information; they were also given the Wisconsin Card Sorting Test (WCST), a test of verbal fluency, and other psychometric tests. The degree of source amnesia in this normal sample correlated with age, verbal fluency, and some measures from the WCST. Source amnesia was not related to Performance IQ, however, or to a measure of fact recall. The implications for the relations among aging, memory, and frontal lobe functions are discussed.

Age Factors↗