Some more recent lines of research converge on claiming that human cognitive behavior in general and linguistic discourse in particular cannot reasonably be reduced to one monolithic system of cognitive activity. What this research suggests, rather, is that this behavior exhibits a dualistic organization. In the present paper, two frameworks representing this tradition are contrasted, namely Discourse Grammar and the dual process model. The former rests on observations on language structure and language use, while the latter was developed on the basis of neurolinguistic observations. The two frameworks converge on claiming that there is a significant correlation between linguistic categorization and hemisphere-based brain activity. The present paper argues that this correlation can be related to contrasting linguistic functions associated with each of the two hemispheres.

Theory of mind (ToM) is a crucial aspect of social cognition and is mediated by a complex neural network. Studies on temporal lobe epilepsy (TLE) suggest that its neuropathological involvement includes several brain regions. Some regions seem to overlap the neural network responsible for ToM, and this overlap provides an opportunity to explore ToM in TLE patients. Another concern is psychosocial problems in TLE, and the study of ToM in TLE could serve as a basis for further understanding the nature of such psychosocial disturbances. Studies on whether TLE patients evidence ToM deficit, however, are scant and controversial. Consequently, we examine whether ToM deficit is evident in TLE. Thirty-one TLE patients and 24 matched controls were recruited and completed four tasks measuring different levels of ToM: false belief, faux pas recognition, processing of implied meanings, and cartoon ToM. The patients were impaired in both basic and advanced ToM. Right TLE had a more wide-ranging picture of deficit than left TLE. ToM appears to be vulnerable to TLE, especially on the right side. Since ToM might contribute to patients’ psychosocial adjustment, we thus suggest that a ToM measure be included in regular neuropsychological assessments of such patients. (JINS, 2013, 19, 1–7)

Patterns of cerebral asymmetry related to visuospatial functions may change with age. The typical leftward bias on a line bisection task may reflect cerebral asymmetry. With age, such leftward bias decreases. This study demonstrated that the age-related decrease of leftward bias may actually be sex-specific. In addition, previous research suggests that young adults’ deviation in line bisection may reflect asymmetric hemispheric activation of perceptual–attentional “where” spatial systems, rather than motor-intentional “aiming” spatial systems; thus, we specifically fractionated “where” and “aiming” bias of men and women ranging in age from 22 to 93 years old. We observed that older men produced greater rightward line bisection errors, of primarily “where” spatial character. However, women's errors remained leftward biased, and did not significantly change with age. “Where” spatial systems may be linked to cortico-cortical processing networks involving the posterior part of the dorsal visuospatial processing stream. Thus, the current results are consistent with the conclusion that reduced right dorsal spatial activity in aging may occur in the male, but not female, adult spatial system development. (JINS, 2011, 17, 455–462)

Metaphors are a fundamental aspect of human cognition. The major neuropsychological hypothesis that metaphoric processing relies primarily on the right hemisphere is not confirmed consistently. We propose ways to advance our understanding of the neuropsychology of metaphor that go beyond simple laterality. Neuropsychological studies need to more carefully control confounding lexical and sentential factors, and consider the role of different parts of speech as they are extended metaphorically. They need to incorporate recent theoretical frameworks such as the career of metaphor theory, and address factors such as novelty. We also advocate the use of new methods such as voxel-based lesion-symptom mapping, which permits precise and formal tests of hypotheses correlating behavior with lesions sites. Finally, we outline a plausible model for the neural basis of metaphor. (JINS, 2010, 16, 1–5.)

Studies of patients with brain damage, as well as studies with normal subjects have revealed that the right hemisphere is important for recognizing emotions expressed by faces and prosody. It is unclear, however, if the knowledge needed to perform recognition of emotional stimuli is organized by modality or by the type of emotion. Thus, the purpose of this study is to assess these alternative a priori hypotheses. The participants of this study were 30 stroke patients with right hemisphere damage (RHD) and 31 normal controls (NC). Subjects were assessed with the Polish adaptation of the Right Hemisphere Language Battery of Bryan and the Facial Affect Recognition Test based on work of Ekman and Friesen. RHD participants were significantly impaired on both emotional tasks. Whereas on the visual-faces task the RHD subjects recognized happiness better than anger or sadness, the reverse dissociation was found in the auditory-prosody test. These results confirm prior studies demonstrating the role of the right hemisphere in understanding facial and prosodic emotional expressions. These results also suggest that the representations needed to recognize these emotional stimuli are organized by modality (prosodic-echoic and facial-eidetic) and that some modality specific features are more impaired than others. (JINS, 2006, 12, 774–781.)

While language facility was once considered to be the sole province of the “dominant” left hemisphere, clinical and experimental findings suggest the right hemisphere plays an equally important role in many language tasks. To elucidate differential hemispheric language processes, Right Hemisphere Language Battery and Western Aphasia Battery data from left (LHD) and right (RHD) hemisphere cerebral vascular accident (CVA) patients and controls were subjected to multivariate discriminant analysis. The highly significant group differences and overall 95% classification rate obtained confirms the utility of the dependent measures in differential diagnosis. Results suggest CVA patients experience disparate language deficits, with the LHD group experiencing concordant-convergent language deficits and the RHD group displaying discordant–divergent deficits that interfere with the receptive and expressive language skills necessary for successful social discourse. (JINS, 2001, 7, 655–664.)

Patients with left spatial neglect following right hemisphere damage may show anomalies in ipsilesional-limb movements directed to targets on their affected side, in addition to their characteristic perceptual deficits. In this study we examined the extent to which visually guided movements made by neglect patients are susceptible to interference from concurrent visual distractors on the contralesional or ipsilesional side of a designated target. Eleven right hemisphere patients with visual neglect, plus 11 matched healthy controls, performed a double-step movement task upon a digitizing tablet, using their ipsilesional hand to respond. On each double-step trial the first component of the movement was cued to a common central target, whereas the second component was cued unpredictably to a target on either the contralesional or ipsilesional side. On separate trials lateral targets either appeared alone or together with a concurrent distractor in an homologous location in the opposite hemispace. In addition to being significantly slower and more error prone than controls, neglect patients also exhibited a number of interference effects from ipsilesional distractors. They often failed to move to left targets in the presence of a right-sided distractor, or else they moved to the distractor itself rather than to a contralesional target. The initial accelerative phase of their movements to contralesional targets tended to be interrupted prematurely, and they spent significantly more time in the terminal guidance phase of movements to contralesional targets in the presence of an ipsilesional distractor. In contrast, contralesional distractors had little effect on patients' movements to ipsilesional targets. We conclude that right hemisphere damage induces a competitive bias that favors actions to ipsilesional targets. This bias affects multiple stages of processing within the visuomotor system, from initial programming through to the final stages of terminal guidance. (JINS, 2001, 7, 334–343)

Arithmetical reasoning ability has been investigated in a group study of patients with unilateral cerebral lesions. Two series of 38 and 39 patients, who had suffered unilateral cerebral lesions of the right and left cerebral hemisphere, respectively, were investigated. They completed a neuropsychological battery that included a test of computation (Graded Difficulty Arithmetic, GDA; Jackson & Warrington, 1986), and a new test of numerical series completion (Arithmetical Reasoning Test, ART). Whereas the left-hemisphere lesion group were markedly more impaired on the GDA compared to both the right-hemisphere lesion group and a standardization sample, both lesion groups were equally severely impaired on the ART. It is suggested that the abstraction of numerical relations, which is essential to numerical series completion, relies on the integrity of the right hemisphere. A global model of arithmetic processing that incorporates these findings is proposed. (JINS, 1997, 3, 260–268.)