Alan B. Rubens

Preserved priming of novel objects in patients with memory disorders

Amnesic patients perform poorly on explicit memory tests that require conscious recollection of recent experiences, but frequently show preserved facilitations of performance or priming effects on implicit memory tasks that do not require conscious recollection. We examined implicit memory for novel visual objects on an object decision test in which subjects decide whether structurally possible and impossible objects could exist in three-dimensional form. Patients with organic memory disorders showed robust priming effects on this task---object decision accuracy was higher for previously studied objects than for nonstudied objects---and the magnitude of priming did not differ from matched control subjects or college students. However, patients showed impaired explicit memory for novel visual objects on a recognition test. We argue that priming is mediated by the structural description system, a subsystem of the perceptual representation system, that operates at a presemantic level and is preserved in amnesic patients.

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.

Memory Impairment and Executive Control in Individuals with Stroke-Induced Aphasia

The purpose of this study was to examine memory abilities of aphasic individuals in relation to site of neurological lesion. Fourteen individuals with stroke-induced aphasia (7 with anterior lesions; 7 with posterior lesions) and 14 demographically matched control subjects were given selected tests of short-term memory (STM) and long-term memory (LTM). Stroke patients were impaired relative to control subjects on tests of verbal memory, with greater impairment of LTM associated with anterior lesions and greater impairment of STM associated with posterior lesions. Verbal memory performance did not correlate highly with language ability, and did not appear to be simply a consequence of language impairment. Executive control deficits were postulated as explanatory of the LTM impairment associated with anterior lesions.

False Recognition and Misidentification of Faces Following Right Hemisphere Damage

We report two patients who, following massive damage to the right hemisphere, showed a striking tendency for false recognition and misidentification of faces. Neuropsychological investigations revealed that excessive reliance on a feature-based left hemisphere strategy in face processing, combined with an inability to evaluate critically the output generated by the dysfunctional face recognition system, played a major role in the recognition errors and misidentifications. Our findings suggest that the feature based left hemisphere face recognition system is potentially error-prone, presumably because component facial features are likely to be shared among several different individuals, and that reliable recognition and identification of faces is critically dependent upon the efficient processing of configurational facial information by the right hemisphere. We propose further that decision making and monitoring functions relevant to the operations of the face recognition system are primarily lateralized to the right frontal lobe.

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 patients 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.

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 non words 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.

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.

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.

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.

Computed Tomographic Scanning and New Perspectives in Aphasia

Classical theories of aphasia are based on detailed studies of very small numbers of patients whose brains came to postmortem examination. Following the introduction of computed tomography (CT), a wealth of clinical-radiographic observations became available and prompted a major reexamination of how language is represented in the brain. Although early CT studies attempted primarily to confirm classical theory (Mazzocchi & Vignolo, 1979; Kertesz, Harlock, & Coates, 1979; Naeser & Hayward, 1978; Damasio & Damasio, 1980), more recent studies have begun to revise concepts of language representation in the brain (Selnes, Knopman, Niccum, Rubens, & Larson, 1983; Seines, Niccum, Knopman, & Rubens, 1984; Seines, Knopman, Niccum, & Rubens, 1985; Knopman et al., 1983; Knopman, Seines, Niccum, & Rubens, 1984; Mohr et al., 1978; Basso, LeCours, Moraschini, & Vanier, 1985).