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Biomedical subjects

F Newcombe

Publications and source records attributed to F Newcombe.

At least 19 recordsLinked to original sources
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↗
PubMed1987

Dissociable visual and spatial impairments following right posterior cerebral lesions: clinical, neuropsychological and anatomical evidence.

A double dissociation of visual and spatial performance is reported in two men with chronic focal missile injuries of the right cerebral hemisphere. The clinical, neuropsychological and post-mortem anatomical data are considered in relation to evidence from physiological research of two major cortico-cortical pathways for object-recognition and spatial perception.

Brain Mapping↗
PubMed1987

A left hemisphere contribution to visuospatial processing.

Men with chronic, focal, unilateral missile injures of the brain--twenty-five with left hemisphere lesions (LH group) and twenty with right hemisphere lesions (RH groups)--and twenty-two control subjects were given two visuoperceptual and two visuospatial tests. The LH group was significantly impaired in relation to the control group on both the spatial tasks. A different pattern of dissociable perceptual and spatial deficits was found in the experimental groups: better preserved perceptual than spatial performance was observed more frequently in the LH group whereas the converse--relatively better spatial than perceptual performance--was more evident in the RH group. Double dissociations in performance on the two spatial tasks were found predominantly in the LH group. These findings suggest an important left hemisphere contribution to visuospatial processing and the possibility of a more focal representation of spatial abilities in the left hemisphere than in the right.

Aged↗
PubMed1987

Faces interfere with name classification in a prosopagnosic patient.

Since sustaining a severe closed head injury P.H. has been completely unable to recognise familiar faces, but remains able to identify written names. Despite his inability to recognise faces overtly, P.H. nevertheless shows a normal pattern of interference from simultaneously presented distractor faces in a politician vs nonpolitician name classification task. His reaction times for semantic (politician versus nonpolitician) classification of printed names are slowed by the presence of a face drawn from the incorrect semantic category. This interference is found even though P.H. performs at chance level when asked to overtly classify the faces used in the task. The finding demonstrates that prosopagnosic patients may covertly achieve relatively precise recognition of familiar faces and access to semantic information.

Adult↗
PubMed1985

Neuropsychology qua interface.

This paper focuses on the multidisciplinary nature and requirements of neuropsychology. It illustrates two approaches to this convergence of neuropsychology and its complementary disciplines: the relationship between the dissociated visual-perceptual and spatial disorders consequent upon focal lesions of the right cerebral hemisphere in man and the evidence (neuroanatomical, neurophysiological, and behavioural) of two major cortico-cortical pathways for processing visual information in monkey; and the evolution of information-processing models (derived from cognitive psychology, linguistics, and pathophysiological data) to delineate the functional architecture of reading and speech production. It cites the study of attention and frontal-lobe function as a major target for research; and it invokes the need to encompass the art of medicine in neuropsychological research and practice.

Animals↗
PubMed1978

Clinical and anatomic findings in a case of auditory agnosia.

A case is reported of severe agnosia for verbal and nonverbal sounds in a setting of well-preserved intelligence and transient dysphasic symptoms. The lesions responsible for this disorder were bilateral cerebral infarcts, one of which had virtually destroyed the areas of Wernicke and Broca. The relation between lesions and disabilities is discussed and comparisons made with other published cases.

Aged↗