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Biomedical subjects

B Milner

Publications and source records attributed to B Milner.

At least 19 recordsLinked to original sources
PubMed2001

A cross-linguistic PET study of tone perception in Mandarin Chinese and English speakers.

PET was used in a cross-linguistic study to determine whether neural mechanisms subserving pitch perception differ as a function of linguistic relevance. We compared tone perception in 12 native Mandarin speakers, who use tonal patterns to distinguish lexical meaning, with that of 12 native speakers of a nontone language, English. Subjects were scanned under two conditions: a silent resting baseline and a tonal task involving discrimination of pitch patterns in Mandarin words. Both groups showed common regions of CBF increase, but only Mandarin speakers showed additional activation in frontal, parietal, and parieto-occipital regions of the left hemisphere; this latter finding indicates that language experience may influence brain circuitry in the processing of auditory cues. In contrast, only the English group showed activity in the right inferior frontal cortex, consistent with a right-hemispheric role in pitch perception.

Brain↗
PubMed2001

Teaching undergraduates about familial breast cancer: comparison of a computer assisted learning (CAL) package with a traditional tutorial approach.

We have developed a computer assisted learning package for teaching clinical medical students about familial breast cancer. It explains the principles of genetic predisposition to breast cancer, the association with other cancers, the principles of family history taking and confirmation, risk assessment and possible interventions. Clinical medical students were randomised to either conventional teaching or CAL, 48 students attended the evaluation session. Students randomised to conventional teaching received a 20 min mini-lecture, those randomised to CAL completed the package with technical, but not academic support available. At the end of the intervention both groups of students completed a short written assessment of acceptability and knowledge and understanding of breast cancer genetics. There was no significant difference between the CAL and mini-lecture groups in terms of marks or acceptability. Thus CAL appears to be an acceptable and effective method of teaching clinical medical students about familial breast cancer. Although time consuming to develop, CAL can be used in a variety of settings to increase curriculum flexibility. Methods of motivating students to complete the CAL, and of providing educational support are being explored.

Breast Neoplasms↗
PubMed2000

Loss of recent memory after bilateral hippocampal lesions. 1957.

Bilateral medial temporal lobe resection in man results in a persistent impairment of recent memory whenever the removal is carried far enough posteriorly to damage portions of the anterior hippocampus and hippocampal gyrus. This conclusion is based on formal psychological testing of nine cases (eight psychotic and one epileptic) carried out from one and one-half to four years after operation. The degree of memory loss appears to depend on the extent of hippocampal removal. In two cases in which bilateral resection was carried to a distance of 8 cm posterior to the temporal tips the loss was particularly severe. Removal of only the uncus and amygdala bilaterally does not appear to cause memory impairment. A case of unilateral inferior temporal lobectomy with radical posterior extension to include the major portion of the hippocampus and hippocampal gyrus showed no lasting memory loss. This is consistent with Milner and Penfield's negative findings in a long series of unilateral removals for temporal lobe epilepsy. The memory loss in these cases of medial temporal lobe excision involved both anterograde and some retrograde amnesia, but left early memories and technical skills intact. There was no deterioration in personality or general intelligence, and no complex perceptual disturbance such as is seen after a more complete bilateral temporal lobectomy. It is concluded that the anterior hippocampus and hippocampal gyrus, either separately or together, are critically concerned in the retention of current experience. It is not known whether the amygdala plays any part in this mechanismi, since the hippocampal complex has not been removed alone, but always together with uncus and amygdala.

Amnesia↗
PubMed1999

Cerebral organization in bilinguals: a PET study of Chinese-English verb generation.

Positron emission tomography (PET) was used to investigate cerebral organization in seven subjects who had Mandarin Chinese as their native language (L1), and learned English (L2) later in life. When activation from word repetition was subtracted from verb generation in L1 and L2, CBF increases were observed for both languages in left inferior frontal, dorsolateral frontal, temporal and parietal cortices, and right cerebellum. Direct comparison of the difference between verb generation and word repetition in L1 and L2 revealed no significant differences. Within-subject analysis of verb generation minus word repetition yielded CBF increases in left frontal cortex for all individuals for L1 and L2, and a comparison of differences yielded no spatial separation in frontal peaks. We argue for shared neural substrates even for such contrasting languages as Mandarin and English.

Adolescent↗
PubMed1999

A cognitive activation study of memory for spatial relationships.

Twelve neurologically normal right-handed subjects were asked to remember the locations of eight representational drawings, presented one at a time, together with two landmarks (white squares), on a computer screen. Subjects were then scanned using positron emission tomography (PET) while performing forced-choice recognition of object location in four conditions, using either the original landmarks or two of the other objects as cues. In two conditions, the absolute location of the objects was unchanged from the time of encoding (fixed-array conditions), whereas in the other two, the location of the objects was shifted, although the spatial relationship among the objects and landmarks was maintained (shifted-array conditions). Subjects were also scanned in a control condition that made the same perceptual and motor demands as the recognition tasks but that had no mnemonic component. Compared to the control condition, all of the recognition tasks activated both the dorsal and ventral visual pathways bilaterally, but with notable asymmetries. In particular, activation in the right, but not left, inferior temporal gyrus (area 37) was observed when both shifted-array conditions were compared to their respective cue-matched fixed-array conditions. The recognition conditions with landmark cues were associated with focal increases in regional cerebral blood flow (rCBF) in the region of the right parahippocampal gyrus. The results support previous reports of involvement of the right mesial temporal region in object-location memory tasks, and suggest that right inferotemporal cortex is involved in extracting the invariant relational features of a visual scene.

Adult↗
PubMed1997

Right medial temporal-lobe contribution to object-location memory.

An important aspect of normal human memory, and one humans share with many other species, is the ability to remember the location of objects in their environment. There is by now strong evidence from the study of epileptic patients undergoing brain surgery that right temporal-lobe lesions that encroach extensively upon the hippocampal and parahippocampal gyrus impair the delayed, but not the immediate, recall of the location of objects within a random array. These findings have now been extended to a multiple-trial, spatial-array learning task; by including not only patients tested after unilateral anterior temporal lobectomy but also those with a selective left or right amygdalohippocampectomy, it has been shown that the deficits associated with right hippocampal lesions are not dependent upon conjoint damage to the lateral temporal neocortex. Furthermore, the fact that on the learning task no group differences were seen on Trial 1, at zero delay, strengthened the view that the impairment was in the maintenance and subsequent retrieval of information rather than in its initial encoding. These results left unresolved the question of whether the deficit was in the mediation of object-place associations or whether it could be reduced to a more general impairment in memory for location as such. Also left unanswered was the neuroanatomical question as to the relative contributions of the hippocampus and the parahippocampal gyrus to the performance of the experimental tasks. These questions were addressed in two blood-flow activation studies that made use of positron emission tomography (PET) and magnetic resonance imaging (MRI) and incorporated computerized versions of object-location and simple-location memory tasks. Taken together, the results point to a special contribution from the anterior part of the right parahippocampal gyrus, probably corresponding to the entorhinal cortex, to the retrieval of object-place associations, a result consonant with neurophysiological findings in non-human primates.

Hippocampus↗
PubMed1997

Obligatory role of the LIFG in synonym generation: evidence from PET and cortical stimulation.

We report results from a patient in whom we obtained converging evidence from positron emission tomography (PET) and intraoperative stimulation mapping to support a one-way dissociation between the functional areas involved in word repetition and synonym generation. Intraoperative stimulation mapping interfered with synonym generation but did not disturb word repetition at the same left inferior frontal site at which a cerebral blood flow (CBF) increase had been observed for a synonym generation task. The results for this single subject suggest that the functional areas involved in different aspects of linguistic processing are dissociable and that specific disruption under conditions of cortical stimulation can be correlated with the brain regions identified via PET as the most active during performance of a specific task.

Adult↗
PubMed1996

Memory for object features versus memory for object location: a positron-emission tomography study of encoding and retrieval processes.

Regional cerebral blood flow was measured with positron-emission tomography during two encoding and two retrieval tasks that were designed to compare memory for object features with memory for object locations. Bilateral increases in regional cerebral blood flow were observed in both anterior and posterior regions of inferior temporal cortex and in ventral regions of prestriate cortex, when the condition that required retrieval of object locations was subtracted from the condition that required retrieval of object features. During encoding, these changes were less pronounced and were restricted to the left inferior temporal cortex and right ventral prestriate cortex. In contrast, both encoding and retrieval of object location were associated with bilateral changes in dorsal prestriate and posterior parietal cortex. Finally, the two encoding conditions activated left frontal lobe regions preferentially, whereas the two retrieval conditions activated right frontal lobe regions. These findings confirm that, in human subjects, memory for object features is mediated by a distributed system that includes ventral prestriate cortex and both anterior and posterior regions of the inferior temporal gyrus. In contrast, memory for the locations of objects appears to be mediated by an anatomically distinct system that includes more dorsal regions of prestriate cortex and posterior regions of the parietal lobe.

Adolescent↗
PubMed1996

Ascertainment of familial ovarian cancer in the Aberdeen Genetic Clinic.

Ovarian cancer is the fifth most common malignancy in women in the UK. Patients with a family history including ovarian cancer make up nearly 15% of family cancer referrals to the Genetic Clinic in Aberdeen. To date, only one pedigree has been suitable for linkage studies, which has enabled us to target screening more accurately at those people at highest risk. Following discovery of a strong candidate for the BRCA1 gene, direct mutation testing may soon be possible. People who seek testing will require further counselling. Therefore we anticipate an increased demand on both clinical and laboratory resources, but more accurate ascertainment of high risk subjects should lead to more appropriate targeting of screening services.

Adult↗
PubMed1995

The neural substrates underlying word generation: a bilingual functional-imaging study.

We used positron emission tomography to investigate word generation in subjects whose first language was English but who were also proficient in French. These subjects performed three types of lexical search: rhyme generation based on phonological cues, synonym generation requiring a semantic search, and translation involving access to a semantic representation in the other language. Two control tasks required word repetition in each language. We investigated whether phonological and semantic word-generation activate similar regions and whether the same neural substrates subserve the second language as subserve the first. A series of cerebral blood flow increases, corresponding to Brodmann's areas 47, 46, 45, and 8, were observed in the left frontal cortex when the baseline repetition task was subtracted from each of the respective generation tasks. The results suggest that common neural substrates are involved in within- and across-language searches and that the left inferior frontal region is activated irrespective of whether the search is guided by phonological or semantic cues.

Acoustic Stimulation↗
PubMed1995

The effects of frontal- or temporal-lobe lesions on susceptibility to interference in spatial memory.

Patients with unilateral frontal- or temporal-lobe lesions and normal control subjects studied multiple arrays of pictures and were tested for recall of the locations of the pictures. One condition consisted of three trials of the same pictures in different spatial arrangements, recall being tested immediately after each presentation. In a second condition (using different stimuli), the subject was given two trials with one set of pictures, but a new set of pictures was viewed on the third trial. All groups showed a build-up of proactive interference across trials using the same pictures, and a release of proactive interference when they studied new pictures. Patients with frontal-lobe lesions were more susceptible to proactive interference than were the other groups.

Adolescent↗
PubMed1995

Recall of self-generated arm movements by patients with unilateral cortical excisions.

In previous work, Leonard and Milner (Neuropsychologia, 29, 47-58, 1991) demonstrated that patients with large excisions from the right frontal lobe have difficulty in reproducing accurately the extent of examiner-defined arm movements, the displacements being made without the aid of vision. The impairment in the right frontal-lobe group was not dependent on recall-condition, being apparent irrespective of the presence of a delay, suggesting that the deficit was primarily one of encoding. We then went on to show that these same patients have a short-term memory deficit when recalling terminal position of examiner-defined arm movements (Neuropsychologia 29, 629-640, 1991). From these investigations we concluded that the right frontal lobe is critically involved in the monitoring of information related to movement. In the present study 58 patients with unilateral temporal- or frontal-lobe excisions were tested on two kinesthetic tasks that required the subjects themselves to select terminal positions, or movement extents, thereby reducing dependence on peripheral feedback. Patients with right frontal-lobe lesions could reproduce these self-generated movements normally, indicating that when demands on feedback are reduced the frontal-lobe contribution is not critical.

Adolescent↗
PubMed1994

Left putaminal activation when speaking a second language: evidence from PET.

The neural representation of the languages of the polyglot speaker has been highly controversial. We used positron emission tomography (PET) to investigate whether production in a second language (L2) involves the same neural substrates as that of a first language (L1) in normal bilingual subjects who learned L2 after the age of 5 years. Comparison of cerebral blood flow (CBF) when repeating words in L2 and repeating words in L1 yielded only a single significant CBF change: an increase in the left putamen. We hypothesize that this region plays a specific role for articulation in L2. The role of the putamen in articulation is supported by foreign accent syndrome (FAS), which can occur after left putaminal damage. The increased articulatory demands imposed by speaking a second language may require complex motor control for speech production in L2.

Adult↗