Biomedical subjects

E H de Haan

Publications and source records attributed to E H de Haan.

7 recordsLinked to original sources

PubMed1995

[The Mini Mental Status test inadequate as screening test for cognitive deterioration in a neurological department].

OBJECTIVE: To study the validity of the Mini-mental state (MMS) in a neurological population. DESIGN: Comparing the results of a neuropsychological examination and the MMS score. SETTING: Departments of Neurology/Neuropsychology of the University Hospital Leiden. METHODS: One hundred and forty-seven patients participated in the study. One hundred and eight patients were classified into two diagnostic groups according to the deterioration index (obtained from test results of the neuropsychological examination) and DSM-III-R criteria: 63 patients had dementia, 45 did not; the other 39 patients were found to have specific cognitive impairments and were excluded from the group comparisons. The discriminative powers of the deterioration index and the MMS were compared; sensitivity and specificity were determined with several cut-off scores of the MMS. RESULTS: The MMS had limited power to discriminate between demented and non-demented patients. The MMS score was strongly related to premorbid intelligence, occupational level and age. Increasing the original cut-off score to 25 points improved sensitivity and specificity to 79% and 84% respectively (with the original cut-off level these were 68% and 93%). CONCLUSION: The diagnostic value of the MMS is limited, especially in patients for whom a correct diagnosis is most relevant.

Aged↗

PubMed1994

Recognition impairments and face imagery.

We investigated face imagery for H.J.A. and P.H., who experience profound difficulties in recognising familiar faces. H.J.A.'s problems involve a perceptual impairment that compromises the integration of features into a coherent representation, and he does not show covert recognition of faces in indirect tests. In contrast, P.H. has shown extensive covert recognition effects, leading to the suggestion that his deficit occurs at a higher level of visual processing than H.J.A.'s. H.J.A. and P.H. were given tasks intended to explore their ability to answer questions that depended on imaging single faces, and on configuration-based or feature-based comparisons of imaged sets of three faces. For all of these face imagery tasks, P.H.'s overall performance was severely impaired. H.J.A., though, showed preserved face imagery when imaging single faces and when making feature-based comparisons between imaged faces. However, when configuration-based comparisons were demanded H.J.A. also showed a severe and stable impairment of face imagery. These observations are inconsistent with the idea that face recognition impairments have a unitary underlying cause and vary only in severity. Instead, they imply multi-stage causation, with the nature of consequent impairments of face imagery being determined by the level at which the recognition deficit arises.

Adult↗

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↗

PubMed1993

Syllabic compression and speech intelligibility in hearing impaired listeners.

Syllabic compression has not been shown unequivocally to improve speech intelligibility in hearing-impaired listeners. This paper attempts to explain the poor results by introducing the concept of minimum overshoots. The concept was tested with a digital signal processor on hearing-impaired subjects. The results show that moderate syllabic compression may raise speech intelligibility, as long as overshoots are minimized and relatively short time constants are used. Frequency equalization also contributes to speech intelligibility.

Acoustic Stimulation↗

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↗