Hiram Brownell

Inference deficits in right brain-damaged patients.

The inferential reasoning ability of right hemisphere-damaged (RHD) patients was tested by presenting pairs of sentences which were to be treated as single, integrated units. The two sentences treated together made one interpretation likely (a correct inference); one of the sentences in isolation encouraged a different interpretation (an incorrect inference). The position of the misleading sentence was systematically varied. Results showed that, in contrast to normal controls, RHD patients have more trouble answering inference questions, especially those concerning incorrect inferences, than answering questions about the factual content of the passages. Also, RHD patients made significantly more errors when the misleading information was contained in the first rather than in the second sentence; this finding indicates that these patients have difficulty revising previously acquired knowledge in light of new information. These results suggest the impairment of several components of normal discourse processing subsequent to right hemisphere brain damage.

Surprise but not coherence: Sensitivity to verbal humor in right-hemisphere patients ☆

Verbal humor deficits were investigated in right-hemisphere-damaged patients. It was hypothesized that the appreciation of jokes presupposes two elements: sensitivity to the surprise element entailed in the punch line of a joke and apprehension of the coherence which results when the punch line has been integrated with the body of the joke. The possible dissociation between these elements was tested by asking subjects to select from four alternatives the appropriate ending to a joke. Right-hemisphere patients exhibited a selective attraction to endings which contained an element of surprise but which were not otherwise coherent with the body of the joke. This finding suggests that right-hemisphere patients have difficulty in integrating content across parts of a narrative and confirms the psychological reality of the proposed distinction between the surprise and coherence elements of humor processing.

Comprehension of humorous and nonhumorous materials by left and right brain-damaged patients.

Right hemisphere-damaged (RHD) and left hemisphere-damaged (LHD) aphasic patients were tested on a nonverbal cartoon completion task that included a humorous (Joke) and a nonhumorous (Story) condition. In both conditions, RHD patients performed worse than LHD patients. More importantly, the qualitative difference between the errors produced by the two groups suggests that right and left hemisphere brain damage impairs different components of narrative ability. RHD patients showed a preserved sensitivity to the surprise element of humor, and a diminished ability to establish coherence. Conversely, LHD patients, when they erred, showed an impaired sensitivity to the surprise element of humor, and a preserved ability to establish coherence by integrating content across parts of a narrative. These results suggest that the observed humor comprehension deficits of RHD patients result specifically from right hemisphere disease and not from brain damage irrespective of locus. The performances of the RHD and LHD patients groups together support a separation of narrative ability from the traditional aspects of language ability typically disrupted in aphasia.

Sensitivity to lexical denotation and connotation in brain-damaged patients: A double dissociation? ☆

Sets of words can be grouped in terms of their denotation (cold and warm both refer literally to temperature) or in terms of their connotation (cold and warm connote remoteness and intimacy, respectively). To assess whether these two facets of meaning are dissociable, unilaterally left- and right-hemisphere-damaged patients were presented with word triads and asked to group together the two words that were closest in meaning. Right-hemisphere-damaged patients showed a preserved sensitivity to denotation, and a selective insensitivity to connotative facets of meanings. In contrast, left-hemisphere-damaged patients exhibited a preserved sensitivity to connotation as well as a selective insensitivity to denotative aspects of meanings. Inasmuch as normal control subjects displayed a flexible sensitivity to both denotative and connotative aspects of meaning, the results suggest that unilateral brain damage selectively curtails use of one or the other major aspect of word meaning.

The semantic deficit hypothesis: Perceptual parsing and object classification by aphasic patients☆

Abstract Many aphasic patients are impaired in their ability to provide or to recognize the names of objects, but little is known about the processing deficits that underlie these difficulties. In this report, a model of object naming/name recognition is proposed, and a prediction is tested concerning one possible functional locus of impairment in name-recognition and object-naming disorders. A subgroup of aphasic patients is found to be impaired in the ability to perform perceptual similarity judgments for pairs of stimulus objects, and to be unable to classify the objects into one of two lexical categories. It is concluded that the classification disorder suffered by these patients results from an impairment at the level of the semantically guided perceptual parsing of objects.

The allocation of memory resources during sentence comprehension: Evidence from the elderly

Two experiments were carried out to examine the ability of elderly subjects to establish syntactically governed dependency relations during the course of sentence comprehension. The findings reveal the manner in which memory constraints operate during syntactic processing.

Discourse Comprehension by Right-Hemisphere Stroke Patients: Deficits of Prediction and Revision

This etymological definition can serve as a useful reminder of some facts that will concern us. The first of these is that the meaning of a conversation does not follow simply from the meanings of the individual sentences that compose it-at least not in the way that the conclusion of a syllogism can be inferred directly from its premises. Instead, it is part of the nature of discourse that it requires a listener who must work to understand how different sentences or utterances are related. (See Chapter 2 for a discussion of the kinds of rules that govern conversations.) To be successful at this kind of understanding entails much more than a knowledge of what individual sentences mean. One must also know when words and sentences depart from their usual functions and how this discrepancy may relate to the speaker’s own purposes or to the subject at hand. Both words and speech acts—declarations, commands, and questions —are like tools in this respect. One can, if one chooses, stir a cup of coffee with a knife; it is also possible to make a joke with a deadpan statement (Millikan, 1984, p. 1).

Theory of mind and the right cerebral hemisphere: Refining the scope of impairment

The neuropsychological and functional characterisation of mental state attribution (“theory of mind” (ToM)) has been the focus of several recent studies. The literature contains opposing views on the functional specificity of ToM and on the neuroanatomical structures most relevant to ToM. Studies with brain-lesioned patients have consistently found ToM deficits associated with unilateral right hemisphere damage (RHD). Also, functional imaging performed with non-brain-injured adults implicates several specific neural regions, many of which are located in the right hemisphere. The present study examined the separation of ToM impairment from other deficits associated with brain injury. We tested 11 patients with unilateral right hemisphere damage (RHD) and 20 normal controls (NC) on a humour rating task, an emotion rating task, a graded (first-order, second-order) ToM task with non-mentalistic control questions, and two ancillary measures: (1) Trails A and B, in order to assess overall level of impairment and set-shifting abilities associated with executive function, and (2) a homograph reading task to assess central coherence skills. Our findings indicate that RHD can result in a functionally specific deficit in attributing intentional states, particularly those involving second-order attributions. Performance on ToM questions was not reliably related to measures of cognitive impairment; however, performance on non-ToM control questions was reliably predicted by Trails A and B. We also discuss individual RHD patients’ performance with attention to lesion locus. Our findings suggest that damage to the areas noted as specialised in neuroimaging studies may not affect ToM performance, and underscore the necessity of combining lesion and imaging studies in determining functional-anatomical relations.

Grammatical class effects in relation to normal and aphasic sentence processing

Agrammatic, Brocas aphasic patients, Wernickes aphasic patients, and neurologically intact control subjects were asked to detect target letters in prose passages and in a scrambled word passage. The targets were embedded, in some instances, in content words (open-class vocabulary items), and in other instances, in function words (closed-class vocabulary items). With respect to the prose passages, both the control subjects and Wernickes aphasic patients were more apt to notice target letters when they appeared in the open-class items than when in closed-class items; by contrast, the agrammatic Brocas patients showed no vocabulary class detection difference. The Wernickes patients were not entirely normal, however: Whereas the normal subjects showed a much smaller vocabulary class effect for letter detection in the scrambled condition, the Wernickes maintained the pattern they had shown in the prose condition. These and other findings obtained on the letter cancellation task are discussed in relation to lexical access mechanisms geared to sentence parsing.

Inference of mental states in patients with Alzheimer's disease

Introduction. The ability to determine what someone thinks or knows often requires an individual to infer the mental state of another person, an ability typi cally referred to as ones “theory of mind”. The present study tests this ability in patients with mild‐to‐moderate Alzheimers disease (AD). Methods. Three theory of mind tests and three standardised neuropsychological tests were presented to a group of patients with AD (n = 25) and a group of healthy elderly controls (n = 15). Results. On the first two theory of mind tasks, the performance of the AD patients was nearly perfect and did not differ from that of the controls: AD patients showed no difficulties in either attributing a false belief to another person, or in recognising their own previous false beliefs. On the third theory of mind task, where the key information was embedded in a story narrative, AD patients per formed significantly worse than controls. However, their performance on this task was similar to the control condition, which used a similar story but which did not involve beliefs. Conclusions. These results, as well as those involving correlations between the neuropsychological tests and performance on the third task, suggest that the AD patients’ difficulty may be secondary to their cognitive impairments, rather than a primary impairment in theory of mind.