Biomedical subjects

F Newcombe

Publications and source records attributed to F Newcombe.

At least 19 recordsLinked to original sources

PubMed1996

Selective loss of verbal imagery.

This single case study of the ability to generate verbal and non-verbal imagery in a woman who sustained a gunshot wound to the brain reports a significant difficulty in generating images of word shapes but not a significant problem in generating object images. Further dissociation, however, was observed in her ability to generate images of living vs non-living material. She made more errors in imagery and factual information tasks for non-living items than for living items. This pattern contrasts with our previous report of the agnosic patient, M.S., who had severe difficulty in generating images of living material, whereas his ability to image the shape of words was comparable to that of normal control subjects. Furthermore, with regard to the generation of images of living compared with non-living material, M.S. shows more errors with living than nonliving items. In contrast, the present patient, S.M., made significantly more errors with non-living relative to living items. There appear to be two types of double dissociation which reinforce the growing evidence of dissociable impairments in the ability to generate images for different types of verbal and non-verbal material. Such dissociations, presumably related to sensory and cognitive processing demands, address the problem of the neural basis of imagery.

Adult↗

PubMed1996

Dissociable contributions of the two cerebral hemispheres to judgments of line orientation.

A previous study of the performance of men with chronic unilateral focal brain lesions (due to wartime missile injury) on a standard test of line orientation suggested a left hemisphere (LH) as well as a right hemisphere (RH) contribution to visuospatial processing. The present study was designed to fractionate the variables that could underlie this unexpected finding and thereby to tease out the mechanisms involved in LH as compared with RH processing. A simpler ("purer") version of the standard line orientation task was used, as were two other versions in which matching in an array and matching with distractors were measured. The findings confirmed the hypothesis of RH involvement in the purer task of metric measurement and suggested that the LH has an important role in keeping track decisions and updating decisions in more complex aspects of line orientation judgment.

Aged↗

PubMed1996

Very late outcome after focal wartime brain wounds.

This paper reviews outcome studies of wartime head-injury in Europe and North America. These include Goldstein's major but neglected contribution. intensive clinical and experimental studies of World War I veterans, in which he emphasizes the need for rehabilitation and community care. The present paper reports a follow-up, in Oxford U.K., of a cohort of World War II veterans drawn from over a thousand head-injured servicemen admitted to St Hugh's Military Hospital in Oxford, usually within one to two days of wounding. This cohort was initially examined in 1963 and thereafter until the present day. Behavioural outcome is remarkably good. Cognitive data show a striking preservation of ability in the group as a whole, despite previously reported selective impairments related to specific loci of lesion. Psychiatric illness is rare; and there is little difference in self-report on rating scales between the veterans and a carefully recruited, age-matched control panel. This positive outcome is attributed to a number of factors, including the psychosocial context of World War II for British servicemen, the expert and systematic medical care that commenced within hours of wounding, and the positive attitude of the civilian population. It reinforces the crucial importance of after-care.

Brain Injuries↗

PubMed1995

Ettlinger revisited: the relation between agnosia and sensory impairment.

The concept of agnosia as a higher order functional impairment, which can occur in the absence of low level visual perceptual deficits, continues to provoke debate. This controversy is complicated by the fact that, on close examination, agnosic patients do tend to have some perceptual difficulties. Thus the issue centres around the question as to whether these deficits play a causal part in the aetiology of agnosia or whether they are functionally independent, with both impairments resulting from the substantial cerebral lesions involved in agnosia. In 1956, Ettlinger published a study in which he compared the performance of patients with visual recognition deficits and patients with posterior brain lesions whose recognition abilities were intact. He argued that visual perceptual problems could not explain the recognition deficit in agnosia as he saw far worse perceptual impairments in patients who did not experience any problems in visual recognition. Although the logic of Ettlinger's argument is not disputed, some criticisms have arisen concerning the study, such as the fact that his experimental group did not include a truly object agnosic patient. In addition, Ettlinger's visual-sensory assessment can no longer be considered comprehensive in the light of present day knowledge of the cerebral visual apparatus. This study therefore investigated three (prosop)agnosic patients and five patients with unilateral brain lesions without recognition deficits on an extensive battery of visual sensory tests. The results support Ettlinger's original claim that (in some cases) agnosia cannot be explained as resulting from lower level visual impairments.

Adult↗

PubMed1994

On the role of parvocellular (P) and magnocellular (M) pathways in cerebral achromatopsia.

We assessed the ability of an achromatopsic patient to detect and discriminate colour and form concealed in a static or dynamic checkerboard display where the luminance differences among adjacent squares were randomly assigned. There were no conditions under which he could discriminate two very different saturated colours from each other. Nevertheless, he could discriminate chromatic from luminance boundaries in static displays when the colour defining the boundary was saturated and the achromatic boundaries all had similar luminance contrast, i.e. varied over a narrow range. However, he could not readily detect chromatic boundaries from among many achromatic boundaries that differed widely in luminance contrast. In addition, he was able to detect chromatic boundaries even when they were concealed by dynamic random luminance masking. His ability to pick out chromatic borders was abolished when desaturated colours were used. However, he was singularly proficient at detecting coloured forms in static or dynamic displays even when the saturation of the colours of which the form was composed were such that they were rendered invisible when concealed as a single square in a checkerboard. This implies that signals about chroma are still available in extracting shape. The patient performed flawlessly when asked to indicate the direction of motion of a horizontal red/green isoluminant grating which was phase shifted by 90 degrees in either direction, demonstrating unequivocally that he has access to the sign of colours that he nevertheless does not perceive.

Brain Diseases↗

PubMed1994

Minor head injury: pathophysiological or iatrogenic sequelae?

This study addresses the possibility that cognitive sequelae--albeit of a transient or minor character--can be associated with mild head injury. Twenty men (aged 16-30 years of age), whose post-traumatic amnesia did not exceed eight hours, were examined within 48 hours of their accident and again one month later. This unselected sample had no previous history of head injury. A control group of 20 men of similar socioeconomic background, was selected from medical wards (where they had been admitted for orthopaedic treatment or a minor operation). They were also retested one month after the first examination. Neuropsychological tests were selected to measure abilities often compromised after significant head injury, namely memory and attention. The experimental component consisted of the fractionation of a complex skill (paced addition) to probe for deficits at different stages of information processing: perception and input into storage; search for and retrieval of information from working memory; and paced and unpaced addition. In general, no significant difference was found between the experimental and control groups, with the possible exception of an initial decrement on two working memory tasks: probe digits and a keeping track task (where the subject has to keep in mind and update a number of variables at the same time). The keeping track paradigm, ostensibly of ecological relevance, may well be worth further exploration in memory research, and in studies of more severely head-injured patients. It is further suggested that the appropriate management and counselling of mildly head-injured patients may help to avert symptoms that are of psychological rather than pathophysiological origin.

Adolescent↗

PubMed1993

Face perception after brain injury. Selective impairments affecting identity and expression.

Current theoretical models of face perception postulate separate routes for processing information needed in the recognition of a familiar face, for matching photographs of unfamiliar faces and for the analysis of facial expressions. The present study investigated this claim in a group of ex-servicemen who had sustained unilateral brain injuries affecting posterior areas of the left or right cerebral hemisphere. Care was taken to confirm the nature of impairment by using two different tasks to assess each of the three theoretically defined abilities (leading to a total of six tasks). We adopted a stringent application of the double dissociation methodology to investigate the pattern of performance across tasks of individual ex-servicemen. A selective impairment was defined as a significantly impoverished performance on both tests of a specific ability, while all other tasks were performed within normal limits. In addition, we used both accuracy and response latency measures to substantiate evidence for spared or defective abilities. The results showed selective impairments of all three abilities on accuracy scores. Response latency data confirmed the finding of a selective deficit in the processing of facial expressions, but produced evidence suggesting that impairments affecting familiar face recognition and unfamiliar face matching were not completely independent from each other in this group of ex-servicemen.

Brain Injuries↗

PubMed1992

Selective loss of imagery in a case of visual agnosia.

Experiments were designed to examine the imagery abilities of an agnosic patient, M.S., who has consistently shown more severe deficits in recognizing visually, and in retrieving knowledge of living as compared with non-living items. Judgements of visual similarity were required for named objects and for object-pictures, as well as for the factual properties of these stimuli. The same disproportionate difficulty in processing living ('natural') objects was found in these tasks as well as in forced-choice recognition. In contrast, no deficit was found on analogous tasks concerned with word-shape similarities. These findings have a bearing on concepts of semantic memory.

Adult↗

PubMed1992

Neuropsychological impairment of face recognition units.

Despite the absence of "conscious", overt identification, some patients with face recognition impairments continue covertly to process information regarding face familiarity. The fact that by no means all patients show these covert effects has led to the suggestion that indirect recognition tasks may help in identifying different types of face recognition impairment. The present report describes a number of experiments with the patient NR, who, after a closed head injury, has been severely impaired at recognizing familiar faces. Investigations mostly failed to show overt or covert face recognition, but NR performed at an above-chance level in selecting the familiar face on a task requiring a forced-choice between a familiar and an unfamiliar face. This discrepancy between a degree of rudimentary overt recognition and absence of covert effects on most indirect tests was addressed using a cross-domain identity priming paradigm. This examined separately the possibility of preserved recognition for faces that NR consistently chose correctly in a forced-choice familiarity decision and those on which he performed at chance level. Priming effects were apparent only for the faces that were consistently chosen as "familiar" in forced-choice. We suggest that NR's stored representations of familiar faces are degraded, so that face recognition is possible only via a limited set of relatively preserved representations able to support a rudimentary form of overt recognition and to facilitate performance in matching and priming tasks.

Adult↗

PubMed1992

Neuropsychology of vision.

A selection of the literature on vision published in the last 2 years from various neuroscience disciplines is reviewed. It is organized around the notion of independent processing mechanisms for sensory cues such as wavelength, intensity and orientation; these are subsequently integrated for the perception of colour, brightness and contours, for example, which then feed into higher order systems for visual recognition (words and objects) and visuospatial cognition. A strict hierarchical system is, however, not plausible. Apart from the physiological evidence against such a concept, the widespread observations of 'knowledge without awareness' suggest direct links between different levels, which by-pass conscious experience.

Attention↗

PubMed1991

A role for the left hemisphere in spatial processing.

This study extended our recently reported evidence of a left hemisphere (LH) contribution to spatial processing on standard visuospatial tasks. The present investigation compared performance on these standard tasks with that on 'purer' experimental tasks. Two tasks of line orientation, two of shape rotation and a shape matching task were administered to 50 men with stable unilateral post-Rolandic missile injuries and 32 control subjects. A LH deficit was found on the standard task of line orientation but not the 'purer' task, suggesting that the LH plays a role in eliminating extraneous information, presented only in the standard test. As for shape rotation, the LH group was impaired on both tasks. On the shape matching task, both experimental groups were significantly slower than control subjects. It is proposed the LH makes an important contribution to mental rotation and the understanding of Euclidean geometrical shapes.

Aged↗

PubMed1991

Covert and overt recognition in prosopagnosia.

Prosopagnosic patients suffer an inability to recognize familiar people by visual inspection of their faces. Despite the absence of overt recognition, though, some prosopagnosic patients continue to process the identities of familiar faces covertly. A longstanding controversy concerns whether the recognition deficit in prosopagnosia is specific for faces, or also affects other types of visual stimuli. We investigated whether the patient P.H., who has severe problems with within-class recognition of many types of visual stimuli, would show covert recognition for all stimuli which he cannot recognize overtly. Such a finding would be consistent with the idea that face recognition and recognition of other visually similar stimuli are performed by the same underlying functional mechanisms. We assessed this possibility with a forced-choice decision between correct and incorrect alternative names for familiar faces, cars and flowers, and with comparisons of P.H.'s ability to learn true versus untrue names to familiar faces, cars and flowers. Results indicated that P.H. does show covert recognition of cars and flowers, as well as faces. In addition, the covert effects observed in the forced-choice name decision and learning tasks used here were shown to have a potential common basis. Finally, the possibility of using covert knowledge as a basis for rehabilitation was explored. As was observed by Sergent and Poncet (1990) in their patient, P.H. could achieve some overt face recognition under very specific circumstances.

Adult↗

PubMed1990

Facial neglect.

Following a stroke, a retired industrial chemist, K.L., complained that faces looked "different" and had become difficult to recognize. Investigation of this problem revealed that it particularly affected the left half of a face as seen by K.L. Defective recognition of this (left) half was found for normal faces, chimaeric faces, and for half-faces presented in isolation, whether upright or inverted. The problem was apparent for both internal and external facial features. Further studies with chimaeric faces demonstrated inattention to left-side features in K.L.'s judgements of facial expression and of resemblance between faces. Moreover, the left-half of a chimaeric face was affected even when it was itself forming part of the face positioned on the right in a display of two horizontally aligned chimaerics. K.L.'s spatial contrast sensitivity function was within normal limits for his age. He did not experience differential difficulty in recognizing the left side of everyday objects or of car-fronts (another stimulus class demanding within-category discrimination between visually similar items that display approximate left-right symmetry). He was also able to sort left or right half-stimuli correctly into the categories "human face", "dog face", or "tree". Although K.L. had a left visual field defect, the problem with faces occurred within otherwise intact parts of his field of vision. We suggest that his disorder can be considered a domain-specific form of unilateral neglect.

Aged↗

PubMed1990

Unawareness of impaired face recognition.

We report investigations of the face processing abilities of SP, a right-handed woman who had suffered a subarachnoid haemorrhage from a right middle cerebral artery aneurysm. Although she could correctly assign visual stimuli to the 'face' category without difficulty, SP performed poorly on all other face processing, tasks, including 'closure' (Mooney faces), perception of facial expression, unfamiliar face matching, and identification of familiar faces. Identification of familiar people from nonfacial cues (names) remained relatively well-preserved, but severe impairments were evident on all face recognition tasks. Her errors mostly involved either failures to find a face familiar at all, or misidentification as another familiar person. In face-name learning tasks, there was evidence of 'covert' recognition of faces she failed to recognize overtly. SP's face processing impairment remained stable across a 20-month period of investigation, yet throughout this period she did not think that she had any problems in face recognition, and continued to show lack of insight into this impairment even when directly confronted with its consequences on formal testing. In contrast, SP showed adequate insight into other physical and cognitive impairments produced by her illness, including poor memory, hemiplegia, and hemianopia. We propose that her lack of insight into her face recognition problems involves a deficit-specific anosognosia, resulting from impairment of domain-specific monitoring abilities.

Agnosia↗

PubMed1989

Face processing, laterality and contrast sensitivity.

Two separate reaction time studies concerning person recognition were conducted with ex-servicemen who incurred unilateral brain injury during the Second World War. The first experiment investigated the ability to construct a facial representation and involved deciding whether a stimulus represented a face or a "non-face" made by repositioning the facial features into an unnatural configuration. Men with posterior right hemisphere (RH) lesions performed this task more slowly than those with left hemisphere (LH) damage and control subjects; the latter two groups did not differ. The second experiment was designed to tap the most basic level of overt person recognition: awareness of familiarity. When faces were used as stimuli, the RH injured group again showed increased response latencies compared with the other two groups. The reverse pattern, slower reaction times for the men with LH lesions with no difference between RH injured and control subjects, emerged when written names were employed. Spatial contrast sensitivity functions were measured in both studies and although both LH and RH injured men showed impaired contrast sensitivity, no hemispheric difference was apparent. Instead, a double dissociation of impairments of contrast sensitivity and face processing was evident.

Adult↗

PubMed1989

Prosopagnosia and object agnosia without covert recognition.

Investigations of the visual recognition abilities of the patient M.S. are reported. M.S. is unable to achieve overt recognition of any familiar faces, and many everyday objects. In Task 1 he showed semantic priming from name primes but not from face primes in a name recognition task. In Task 2 he showed no advantage in learning true (face + correct name) rather than untrue (face + someone else's name) pairings of faces and names. In Task 3 semantic priming of lexical decision was only found for object picture primes that M.S. was able to recognize overtly. In Task 4 faster matching of photographs of familiar than unfamiliar objects was only found for objects that M.S. was able to recognize overtly. These findings demonstrate an absence of covert recognition effects for M.S., consistent with the view that his impairment is primarily "perceptual" in nature.

Adult↗

PubMed1989

Implicit access to semantic information.

Three experiments investigating the patient M.S.'s semantic memory are reported. Experiments 1 and 2 involved a category-membership decision task, in which M.S. was asked to determine whether a noun was a member of a specified semantic category. His performance in Experiment 1 was impaired for nouns from living categories in comparison with nouns from nonliving categories, and this impairment was especially marked for nouns of low typicality. Experiment 2 demonstrated an equivalent pattern of very poor performance to nouns of low familiarity from living categories. In Experiment 3 the effect of a category label on lexical decision was examined, using category labels as primes preceding nouns or pronounceable nonwords. Facilitation from related category label primes was found for typical and untypical members of living and nonliving semantic categories. These findings demonstrate that M.S. has impaired knowledge of the structure of living semantic categories when explicit access to this information is required (Experiments 1 and 2), but that some form of preserved category structure can be demonstrated in tasks which assess this implicitly (Experiment 3).

Agnosia↗

PubMed1987

Left-hemisphere missile injury. A clinical and anatomical case study, with 25-year follow up.

A case is reported of left-hemisphere missile injury sustained in 1944. A stable pattern of selective loss (dysphasia, dyslexia, dysgraphia, and verbal memory impairment) and intact abilities (perceptual and spatial skills and nonverbal memory) was followed up for 25 years. No progressive or generalized intellectual deterioration to suggest interaction between this brain injury and normal aging was observed. The clinical and neuropsychological sequelae are related to the detailed postmortem findings.

Aphasia↗