Biomedical subjects

S Z Rapcsak

Publications and source records attributed to S Z Rapcsak.

At least 37 records · Page 2Linked to original sources

PubMed1993

Implicit and explicit memory following anterior communicating artery aneurysm rupture.

Several tasks examined the status of implicit and explicit memory in three patients with a ruptured anterior communicating artery (ACoA) aneurysm, one patient with bilateral temporal lobe damage sustained from herpes encephalitis (HE), 12 Alzheimer's disease (AD) patients, and 16 elderly normal controls demographically matched to the AD patients. All subjects completed word stem-completion repetition priming, pursuit-rotor tracking, and a fragmented pictures test, followed by explicit memory tests. ACoA, HE, and AD patients were impaired on all explicit tests. HE and AD patients were impaired on stem-completion priming, but were intact on other implicit tests. ACoA patients were intact on all implicit tests given. Discussion of these results considers similarities and differences in extent of basal forebrain and temporal lobe damage.

Adult↗

PubMed1993

Praxis and the right hemisphere.

We report our observations on praxis in a strongly right-handed man following a massive stroke that resulted in virtually complete destruction of the left cerebral hemisphere. Our patient was severely impaired in pantomiming transitive gestures with the left hand and in reproducing novel non-symbolic hand and arm movement sequences. However, overlearned habitual actions like actual object use and intransitive gestures were relatively spared. Performance of axial commands was intact. Gesture recognition and discrimination were also preserved. Based on these findings, we propose that the praxis system of the right hemisphere is strongly biased toward "concrete" or context-dependent execution of familiar, well-established action routines. The right hemisphere is critically dependent on transcallosal contribution from the left hemisphere for control of the left hand in "abstract" or context-independent performance of transitive movements and in learning novel movement sequences. At least in some individuals, the right hemisphere can recognize and discriminate gestures. Possible implications of our findings for the cerebral control of praxis and for recovery from apraxia are discussed.

Aphasia, Broca↗

PubMed1993

Anomia for facial expressions: neuropsychological mechanisms and anatomical correlates.

We report a patient with a selective impairment in naming and pointing to emotional facial expressions following a circumscribed lesion of the right temporal lobe. Detailed investigation of this patient's deficit revealed that the neuropsychological mechanism underlying his anomia for facial expressions is best understood as a category-specific bidirectional visual-verbal disconnection between intact visual semantic and verbal semantic representations for facial emotions. Magnetic resonance imaging findings from this case and from another patient previously described with this unique syndrome (Rapcsak, Kaszniak, & Rubens, 1989), together with the results of cortical electrical stimulation studies and microelectrode recordings of cortical neuronal activity in epileptic patients, provide converging evidence that the inferotemporal visual association cortex of the right middle temporal gyrus plays an important functional role in the verbal labeling of emotional facial expressions. The implications of these findings for cognitive and neural models of facial affect processing are discussed.

Aged↗

PubMed1991

Writing with the right hemisphere.

We studied writing abilities in a strongly right-handed man following a massive stroke that resulted in virtually complete destruction of the language-dominant left hemisphere. Writing was characterized by sensitivity to lexical-semantic variables (i.e., word frequency, imageability, and part of speech), semantic errors in writing to dictation and written naming, total inability to use the nonlexical phonological spelling route, and agrammatism in spontaneous writing. The reliance on a lexical-semantic strategy in spelling, semantic errors, and impaired phonology and syntax were all highly consistent with the general characteristics of right hemisphere language, as revealed by studies of split-brain patients and adults with dominant hemispherectomy. In addition, this pattern of writing closely resembled the syndrome of deep agraphia. These observations provide strong support for the hypothesis that deep agraphia reflects right hemisphere writing.

Agraphia↗

PubMed1990

Disruption of semantic influence on writing following a left prefrontal lesion.

We report a patient with impaired spontaneous writing, written naming, and homophone spelling, consistent with a disruption of semantic influence on writing. However, writing to dictation by both the phonological and lexical spelling systems was intact. In addition, general semantic abilities were spared, as indicated by preserved auditory and reading comprehension. We propose that our patient could not incorporate meaning into writing because of a disruption of both direct and indirect connections between semantics and the orthographic output lexicon. The writing dysfunction was accompanied by a similar impairment of speech output, suggesting that it was part of a more general disturbance of semantic influence on language production following left prefrontal damage.

Anomia↗

PubMed1990

From letters to words: procedures for word recognition in letter-by-letter reading.

There are two alternative interpretations of how word recognition is accomplished in letter-by-letter reading. One postulates that it relies on the spelling system operating "in reverse," whereas the other claims that it is mediated by the reading system. Because of the close association between patterns of reading and spelling in previously reported cases of letter-by-letter reading, both hypotheses may be considered equally plausible. We now report a patient with letter-by-letter reading who demonstrated a striking dissociation between reading and spelling. Our observations in this patient argue against the concept of "reading via spelling" and suggest that word recognition in letter-by-letter reading is mediated by the orthographic input lexicon used in normal reading.

Agraphia↗

PubMed1990

Impaired shifting of attention in Balint's syndrome.

We assessed the efficiency of attentional shifts across the horizontal and vertical axes of the visual field in a patient with Balint's syndrome caused by bilateral parieto-occipital infarctions. This was performed using an adaptation of Posner's peripheral cueing paradigm. In contrast to normal controls and patients with unilateral parietal lesions previously reported, this patient did not benefit from cues directing attention to the left or right visual field. She appeared to benefit only when the cues directed attention to the upper visual field. This suggests a defect in shifting attention that may occur following bilateral parietal lesions. We discuss the implications of these findings for the role of the parietal lobes in attentional processes and for our understanding of the behavioral abnormalities observed in Balint's syndrome.

Adult↗

PubMed1990

Mixed transcortical aphasia without anatomic isolation of the speech area.

We report two patients with mixed transcortical aphasia following left frontal lobe infarctions. Although there was no evidence of anatomic isolation of the speech area on computed tomograms or magnetic resonance imaging scans, single-photon emission computed tomography in one case demonstrated diminished blood flow over the left parietal convexity suggestive of "functional isolation" of the posterior perisylvian language zone.

Aged↗

PubMed1989

Lexical agraphia in Alzheimer's disease.

We studied spelling in 11 patients with senile dementia of the Alzheimer type (SDAT), and their performance was contrasted with that of normal controls. A consistent and specific pattern of linguistic agraphia was identified in the group with SDAT. Although patients with SDAT spelled regular words and nonwords as well as controls, they performed significantly worse when they spelled irregular words. These findings indicated an impairment of the lexical spelling system, consistent with the diagnosis of lexical agraphia. Our observations suggested a loss of word representations from the orthographic lexicon in SDAT and/or an inability to access these representations. However, phonological spelling (phoneme-grapheme conversion) was largely spared.

Aged↗

PubMed1989

Selective attention in hemispatial neglect.

To determine how increasing demands on visual selective attention affect the symptoms of hemispatial neglect, we studied patients with right hemispheric lesions on a cancellation task requiring various degrees of focused attention. In the target only condition, the patients were to cancel all stimuli. In the target-nontarget condition, discriminating targets from nontargets did not require close scrutiny, whereas in the target-foil condition, discriminating targets from foils required greater attention to detail. Our findings indicate that increasing demands on visual selective attention adversely affect both exploration of the left side of space and visual discrimination.

Analysis of Variance↗

PubMed1989

Loss of spontaneous blinking in a patient with Balint's syndrome.

A patient with Balint's syndrome caused by bilateral parieto-occipital lesions lost spontaneous blinking, suggesting that humans, like nonhuman primates, have parietal lobe neurons that are important for blinking. Although the functions of spontaneous blinking are not known, they may help initiate some saccades and, like saccades, be involved in the cancellation of thalamic inhibitory postsynaptic potentials, thereby facilitating processing of new foveal targets. Spontaneous blinking may also facilitate sensory relay during sustained attention and, therefore, help prevent fading of a retinal image.

Adult↗

PubMed1989

Impaired recognition of meaningful sounds in Alzheimer's disease.

We studied recognition of meaningful nonverbal sounds using a sound-picture matching test in 18 patients with senile dementia of the Alzheimer type (SDAT) and 19 age-matched controls. A significant impairment of sound recognition was found in the SDAT group, consistent with auditory sound agnosia. Although sound recognition performance correlated significantly with auditory verbal comprehension scores, a sound recognition defect was also identifiable in the subgroup of patients with SDAT who had normal verbal comprehension. Qualitative analysis of sound recognition errors revealed that nonaphasic patients with SDAT made predominantly acoustic errors, whereas semantic errors were found almost exclusively in aphasic patients. These findings suggest that the auditory sound agnosia of patients with SDAT may be subdivided into perceptual-discriminative and semantic-associative types.

Aged↗

PubMed1989

Anomia for facial expressions: evidence for a category specific visual-verbal disconnection syndrome.

We describe a patient with a selective impairment in naming and pointing to emotional facial expressions following damage to the right temporal lobe. His language functions were otherwise intact, and he performed well on a variety of perceptual and associative emotional facial tasks. We propose that his inability to match facial expressions with their names was induced by a disconnection between visual semantic and verbal semantic representations for facial emotions.

Aged↗

PubMed1989

'Peduncular hallucinosis' following paramedian thalamic infarction.

An 83-year-old man had the sudden onset of vivid formed hallucinations, agitation, and sleep disturbance suggesting "peduncular hallucinosis." A magnetic resonance scan revealed a right paramedian thalamic infarction with no abnormality of the cerebral peduncles or midbrain.

Aged↗

PubMed1989

Apraxia in Alzheimer's disease.

We studied apraxia in 28 patients with senile dementia of the Alzheimer type (SDAT). Although SDAT patients were impaired compared with age-matched controls on tests of ideomotor and ideational apraxia, not all types of movements were affected to the same degree. Limb transitive movements were especially vulnerable, while limb intransitive, buccofacial, and axial movements were relatively spared. When pantomiming limb transitive movements, SDAT patients made frequent body part as object and spatial errors. There was no significant difference between performance on verbal command and imitation, but there was considerable improvement with the use of actual objects. Disorders of skilled movement in SDAT were qualitatively similar to the apraxic syndromes following left parietal damage. Apraxia in SDAT suggests posterior left hemisphere cortical involvement and may be apparent even in patients with good language functions.

Aged↗

PubMed1988

Altitudinal neglect.

Previous clinical observations on patients with hemispatial neglect from unilateral hemispheric lesions suggest the brain's attentional mechanisms are organized along the horizontal dimensions of extrapersonal space. We now report a patient with Balint's syndrome caused by bilateral parieto-occipital infarctions, who demonstrated altitudinal neglect. On visual and tactile bisection of vertical rods, the patient consistently placed her mark well above the true midpoint, and this performance remained unchanged when the stimuli were simultaneously explored visually and tactually. She also showed altitudinal inattention in the visual modality by extinguishing the stimulus presented in the lower quadrants during double simultaneous stimulation across the horizontal meridian. These findings suggest that bilateral damage to the parietal lobes can lead to multimodal attentional and exploratory deficits along the vertical dimensions of extrapersonal space.

Adult↗

PubMed1988

Lexical agraphia from focal lesion of the left precentral gyrus.

Lexical agraphia reflects a dysfunction of the lexical spelling system and is characterized by better spelling of nonwords and regular words than irregular words. All previously reported cases with documented focal lesions had involvement of temporo-parieto-occipital regions. We now report a case of lexical agraphia following a discrete lesion of the left precentral gyrus. Our case complements previous neuroanatomical accounts of agraphia and provides further support for the independence of neuronal systems that mediate spelling from those involved in spoken language and reading.

Aged↗

PubMed1988

Pupil-sparing oculomotor palsy from midbrain hemorrhage.

Pupil-sparing oculomotor nerve palsy generally results from extraaxial lesions, but it has also been seen with intraaxial infarcts and tumors. This report of a midbrain hemorrhage in a 64-year-old man supports the idea of selective interference with widely separated oculomotor nerve fascicles as the mechanism for intraaxial pupil-sparing oculomotor nerve palsies.

Cerebral Hemorrhage↗