Biomedical subjects

Maryse Lassonde

Publications and source records attributed to Maryse Lassonde.

30 records · Page 2Linked to original sources

PubMed2004

Neuropsychology: pitch discrimination in the early blind.

Do blind people develop superior abilities in auditory perception to compensate for their lack of vision? They are known to be better than sighted people at orientating themselves by sound, but it is not clear whether this enhanced awareness extends to other auditory domains, such as listening to music or to voices. Here we show that blind people are better than sighted controls at judging the direction of pitch change between sounds, even when the speed of change is ten times faster than that perceived by the controls--but only if they became blind at an early age. The younger the onset of blindness, the better is the performance, which is in line with cerebral plasticity being optimal during the early years.

Acoustic Stimulation↗

PubMed2004

Effective binocular integration at the midline requires the corpus callosum.

To study the role of the corpus callosum (CC) in midline binocular integration, the effects of late callosotomy and congenital CC agenesis on the ability to perceive dichoptic plaid motion was assessed. Coherent motion was well perceived at all locations in the visual field under dioptic viewing but not along the vertical meridian (VM) when the components were dichoptically presented. This deficit was totally abolished in the agenesis subject and reduced in the callosotomized individual when stimulus size was increased beyond the VM. Electrophysiological correlates were also examined by recording visual evoked potentials and these showed that the P1/N2 components were abnormal for small dichoptic stimuli presented on the midline. These findings attest to the importance of the contribution of CC to midline binocular integration and the effects of cerebral plasticity.

Adult↗

PubMed2004

Visual p300 effects beyond symptoms in concussed college athletes.

In order to assess whether cerebral anomalies may be observed in the absence of clinical symptoms, the current study compared the effects of concussions on attentional capacities (reaction times, accuracy) and Event-Related Potentials (ERPs) in concussed athletes with (n = 10) or without (n = 10) symptoms as well as in athletes who never had a concussion (n = 10). The P300 response was recorded from 28 electrodes during a modified visual oddball paradigm. Participants were instructed to press a key upon the appearance of the frequent stimuli as well as when a rare nontarget stimulus followed the frequent one. The other key was to be pressed when the subsequent rare stimuli (rare target) appeared until a frequent one reappeared. The symptomatic athletes displayed longer reaction times than the other two groups of athletes. The P300 amplitude to the rare target stimuli was significantly more attenuated in the symptomatic athletes than in the other two groups. Moreover, the P300 amplitude varied inversely with the severity of post-concussion symptoms but was not influenced by time elapsed since injury. Although the clinical significance of the P300 differences shown by the symptomatic athletes is still uncertain, the results do indicate that symptom severity may be a crucial indicator of functional impairments following mild traumatic brain injury.

Adult↗

PubMed2004

Inter- and intra-hemispheric processing of visual event-related potentials in the absence of the corpus callosum.

Interhemispheric differences of the N100 latency in visual evoked potentials have been used to estimate interhemispheric transfer time (e.g., Saron & Davidson, 1989). Recent work has also suggested that the P300 component could reflect the efficacy of interhemispheric transmission (Polich & Hoffman, 1998). The purpose of the present study was to study the differential role of the corpus callosum (CC) and anterior commissure (AC) in the interhemispheric propagation of these two electrophysiological components. Thus, the amplitude and latency distribution of the N100 and P300 components were analyzed using high-density electrical mapping in a subject with agenesis of CC but preservation of AC, a subject with agenesis of both CC and AC, and 10 neurologically intact control subjects. The task consisted of a modified visual oddball paradigm comprising one frequent and two rare stimuli, one presented on the same and the other on the opposite side of the frequent stimulus. Interhemispheric differences in latency were found for the N100 component in controls. However, in the acallosal subjects, this component was not identifiable in the indirectly stimulated hemisphere. In controls, no interhemispheric differences were observed in the distribution of the P300 latency and amplitude to rare and frequent stimuli. The distribution of the P300 amplitude in the acallosal subject with an AC was identical to that of the controls, whereas in the acallosal subject lacking the AC, the amplitude was greater in the hemisphere receiving the frequent stimuli, regardless of the visual hemifield in which the rare stimuli were presented. In both acallosal subjects, hemispheric differences in the P300 latency were observed, the latencies being shorter in the hemisphere directly stimulated for all categories of stimuli. These results suggest that the interhemispheric transfer of both the N100 and P300 components relies on the integrity of cortical commissures. Possible P300 generator sources are discussed.

Adult↗

PubMed2003

Attention, memory, and behavioral adjustment in children with frontal lobe epilepsy.

To explore whether attention, memory, and behavior would be more affected in children with frontal lobe epilepsy than in children with other types of epilepsy, we compared 16 children with frontal lobe epilepsy (FLE), 8 with temporal lobe epilepsy (TLE), and 8 with generalized absence (GEA) seizures on the Performance Speed (PS) and Freedom of Distraction (FD) indices of the WISC-III, the Continuous Performance Test (CPT), the California Verbal Learning Test (CVLT), and Rey-Osterrieth Complex Figure (ROCF). Parents completed Achenbach's Child Behavior Check List. Children with FLE scored significantly lower than the other two groups on the PS and CPT. On the CVLT they made more intrusion errors and were more prone to interference. Furthermore, they had more difficulties copying and recalling the ROCF. Behavior profiles revealed greater attention problems in this group. This may put children with FLE at greater risk of developing school problems than children with TLE and GEA.

Adaptation, Psychological↗

PubMed2003

Self-face processing in a callosotomy patient.

Self-face recognition is reserved for humans, apes and possibly dolphins and is thought to be a marker of self-awareness. Previous data have indicated that self-face recognition may be mediated via frontal right hemisphere circuits within the brain. Testing patient M.L., who underwent a total callosotomy, we found that when searching for the self-face in a series of morphs (composite facial images made up of his own and a famous face in inversely varying percentages) the patient made (i) more true-positive and (ii) fewer false-positive responses when responding with the right hemisphere (i.e. indicating with the left hand). There was no hand difference when searching for familiar faces. These data imply a right hemisphere processing advantage for self-faces.

Adult↗

PubMed2002

Deficits in executive functions and motor coordination in children with frontal lobe epilepsy.

Frontal lobe dysfunction in adults has been associated with impairments of planning abilities, working memory, impulse control, attention and certain aspects of motor coordination. However, very few studies have attempted to assess these functions in children suffering from frontal lobe epilepsy. The aim of the present study was to determine whether some or all of the components of the frontal lobe syndrome are present in children with this disorder. For this purpose, a neuropsychological test battery was administered to 32 unresected epileptic children, aged 8-16 years: 16 with frontal lobe epilepsy (FLE), eight with temporal lobe epilepsy (TLE) and eight with generalized epilepsy whose principal manifestations were typical absences (GEA). The performances of the three epileptic groups were further compared to normative data derived from 200 French-speaking, healthy children aged 7-16 years, except for standardized tests for which the norms provided in the manual were used. The three epilepsy groups did not differ with respect to conceptual shift and recency memory. However, the FLE children showed deficits in planning and impulse control. Furthermore, they had significantly more coordination problems and exhibited greater rigidity than the other epilepsy groups on the motor tests. These problems were more marked in younger FLE children (8-12 years). The latter were also more impaired on verbal fluency measures. No differences were observed with respect to gender, localization of the epileptic abnormality (unilateral versus bilateral) or medication (monotherapy versus polytherapy). The findings reveal similarities between the neuropsychological profiles of FLE children and adults with frontal lobe lesions.

Adolescent↗

PubMed2002

Neuropsychological effects of hyperbaric oxygen therapy in cerebral palsy.

We conducted a double-blind placebo study to investigate the claim that hyperbaric oxygen treatment (HBO2) improves the cognitive status of children with cerebral palsy (CP). Of 111 children diagnosed with CP (aged 4 to 12 years), only 75 were suitable for neuropsychological testing, assessing attention, working memory, processing speed, and psychosocial functioning. The children received 40 sessions of HBO2 or sham treatment over a 2-month period. Children in the active treatment group were exposed for 1 hour to 100% oxygen at 1.75 atmospheres absolute (ATA), whereas those in the sham group received only air at 1.3 ATA. Children in both groups showed better self-control and significant improvements in auditory attention and visual working memory compared with the baseline. However, no statistical difference was found between the two treatments. Furthermore, the sham group improved significantly on eight dimensions of the Conners' Parent Rating Scale, whereas the active treatment group improved only on one dimension. Most of these positive changes persisted for 3 months. No improvements were observed in either group for verbal span, visual attention, or processing speed.

Attention↗

PubMed2002

Launching a research initiative: the Canadian Pediatric Epilepsy Network (CPEN).

The Canadian Pediatric Epilepsy Network is a network of scientists and health care professionals in partnership with organizations which provide education and support to children with epilepsy. The objective of the network is to gain a better understanding of childhood epilepsy through collaborative research conducted with doctors, psychologists, nurses, social workers, educators and scientists across Canada. The network was launched at a meeting in Ottawa in the spring of 2000 where several oral presentations addressed the issues of the fundamental questions of epilepsy, the economic impact and the neuropsychology of childhood epilepsy. The intent was to provoke discussion on future areas of research for the network.

Canada↗

PubMed2002

Sound localization in callosal agenesis and early callosotomy subjects: brain reorganization and/or compensatory strategies.

In order to evaluate the callosal involvement in sound localization, the present study examined the response accuracy of acallosal and early callosotomized subjects to monaural and binaural auditory targets presented in three-dimensional space. In these subjects, bilateral localization cues, such as interaural time and level differences, are integrated at the cortical and subcortical levels without the additional support of the callosal commissure. Because acallosal and early-callosotomized subjects have developed with this reduced source of binaural activation of cortical cells, they might have perfected their ability to use monaural sound localization cues. This hypothesis was tested by assessing localization performance under both binaural and monaural listening conditions. Five subjects with callosal agenesis, one callosotomized subject operated early in life and 19 control subjects were asked to localize broad-band noise bursts (BBNBs) of fixed intensity in the horizontal plane in an anechoic chamber. BBNBs were delivered through randomly selected loudspeakers. Two conditions were tested: (i) localization of a stationary sound source; and (ii) localization of a moving sound source. Listeners had to report the apparent stimulus location by pointing to its perceived position on a graduated perimeter. The results indicated that the acallosal subjects were less accurate than controls, but only in the binaural moving sound condition. More interestingly, in the monaural testing conditions, some of the acallosal subjects and the early-callosotomized subject performed significantly better than control subjects. This suggests that, because of the absence of the corpus callosum, these subjects compensate for their reduced access to cortically determined binaural cues by making more efficient use of monaural cues.

Acoustic Stimulation↗

PubMed2002

Verbal cognitive functioning and learning in girls treated for acute lymphoblastic leukemia by chemotherapy with or without cranial irradiation.

Neuropsychological problems have frequently been reported following treatment of Acute Lymphoblastic Leukemia (ALL), however, partly because of the heterogeneity of the previously studied samples, the specific nature of these deficits is still a matter of debate. These problems, however, appear to be related more to the combination of cranial radiation therapy (CRT) and intrathecal chemotherapy (ITC) than to ITC alone. In this study, we evaluated a homogenous group of 19 girls between the ages of 7 and 11 years, 30 months after the completion of treatment. Nine received cranial radiation and chemotherapy and 10 were treated with chemotherapy alone. The patients were compared to 10 normal healthy controls. Neuropsychological tests included the Wechsler Intelligence Scale for Children-Third Edition (WISC-III), the California Verbal Learning Test-Children's Version (CVLT-C), and the Calculation and Passage Comprehension subtests of the Woodcock-Johnson Psycho-Educational Battery-Revised. Results confirmed the presence ofa verbal learning deficit in ALL girls treated with the combination of ITC and CRT. The ITC and CRT group scored significantly lower than the healthy controls on the Passage Comprehension subtest and on 5 of the 6 verbal subtests of the WISC-III. Furthermore, compared to nonirradiated patients and healthy normal controls, the ITC and CRT group was impaired on the Freedom from Distractibility index of the WISC-III, indicating an auditory-verbal attention deficit. On the CVLT-C, the ITC and CRT group was particularly impaired on the second half of the learning trials compared to the other two groups, showing a plateau in their performance. The ITC group was not different from the healthy control group, suggesting a less detrimental effect of the ITC alone on verbal abilities. Globally, these results indicate a deficit affecting auditory attention and verbal learning in girls who receive ITC and CRT, which may suggest the necessity for special educational assistance for these children.

Antineoplastic Combined Chemotherapy Protocols↗

PubMedDate not supplied

Visual object agnosia as a problem in integrating parts and part relations.

Current models of vision generally assume that the recognition of visual objects is achieved by encoding their component parts, as well as the spatial relations among parts. The current study examined how the processing of parts and their configurations may be affected in visual agnosia due to brain damage. Both a visual agnosic patient (AR) and healthy control subjects performed a visual search task in which they had to discriminate between targets and distractors that varied according to whether they shared their parts and/or their configuration. The results show that AR's visual search rates are disproportionally slow when targets and distractors share the same configuration than when they have different configurations. AR is also found to be disproportionately slow in discriminating targets and distractors that share identical parts when the targets and distractors share the same configuration. With differently configured targets and distractors, AR shows no part sharing effect. For controls, in contrast, the part and configuration sharing effects occur independently of one another. It is concluded that AR's object recognition deficit arises from difficulties in discriminating objects that share their configuration, and from an abnormal dependency of part information processing upon object configuration.

Adult↗