Lateral asymmetry in phonological processing: relating behavioral measures to neuroimaged structures

Recent neuroimaging studies have revealed neuroanatomical centers of activation that appear to be linked specifically to phonological processes. Furthermore, there is evidence that these centers of activation are more likely to be bilaterally represented in women than in men. However, behavioral evidence of such hemispheric asymmetries or of related sex differences is somewhat inconsistent. Two experiments were carried out to determine whether behavioral correlates of the neuroimaging findings could be demonstrated. The first experiment employed a rhyme-matching task used in a recent neuroimaging study, in which two nonsense words were projected successively to the left or right sides of the visual field. The results indicated that the left hemisphere was superior for this task. An analysis of gender effects, however, revealed that the asymmetry was restricted to men. The second experiment employed a lateralized pseudohomophone detection task that was designed to determine whether the results of the first experiment could be confirmed in the context of a phonological task with a simpler structure. This experiment broadly supported the findings of the first experiment. The results support the specialization of the left hemisphere for phonological processing, and the existence of gender differences with respect to these processes.     

Effects of right and left hemisphere damage on performance of the "Right Hemisphere Communication Battery"

A Hebrew adaptation of Gardner and Brownell's (1986) "Right Hemisphere Communication Battery" (HRHCB) was administered to 27 right brain-damaged (RBD) patients, 31 left brain-damaged (LBD) patients, and 21 age-matched normal controls. Both patient groups showed deficits relative to controls and overall there was no difference between the two patient groups. A factor analysis of patients' scores on the HRHCB yielded two interpretable factors, a verbal and a nonverbal one. These factors were not lateralized. Performance of patients on the HRHCB correlated significantly and positively with performance on most tests of basic language functions, measured with a Hebrew adaptation of the "Western Aphasia Battery" (HWAB) and with other cognitive functions measured with standardized neuropsychological tests. There were stronger correlations of HRHCB with subtests of the HWAB in LBD patients and with nonlanguage cognitive tests in RBD patients. In the LBD group, HRHCB subtests' scores correlated negatively with lesion extent in frontal and temporal perisylvian regions. Such localization was not observed in RBD patients. The results argue against selective right hemisphere (RH) involvement in the RHCB, alleged to measure pragmatic aspects of language use, and show, instead, bilateral involvement. The results also argue against a modular organization of these functions of language use, especially in the RH.     

Task-related factors in oral motor control: speech and oral diadochokinesis in dysarthria and apraxia of speech

This study was focused on the potential influence of task-related factors on oral motor performance in patients with speech disorders. Sentence production was compared with a nonspeech oral motor task, i.e., oral diadochokinesis. Perceptual and acoustic measures of speech impairment were used as dependent variables. Between-task comparisons were made for subsamples of a population of 140 patients with different motor speech syndromes, including apraxia of speech and cerebellar dysarthria. In a further analysis subgroups were matched for speaking rate. Overall, dysdiadochokinesis was correlated with the degree of speech impairment, but there was a strong interaction between task type and motor speech syndrome. In particular, cerebellar pathology affected DDK to a relatively greater extent than sentence production, while apraxic pathology spared the ability of repeating syllables at maximum speed.     

Neuronal changes in normal human aging and Alzheimer's disease

This article discusses age-related changes in brain weight, total number of cortical neurons, cortical dendrites, spine, and synapse density. The conclusion is that the present outlook is less grim than it was 30 years ago. Age-related reduction appears to be specific to brain region and cortical layer rather than a general feature. In addition, we describe a different pattern of changes that occur in Alzheimer's disease patients. This review concludes that the association cortices in particular are affected in aging and Alzheimer's disease and that the primary visual and somatosensory cortices are relatively spared.     

Paradoxical breathlessness in asthma

This study tested the hypothesis that breathlessness in asthma relates linearly to airway obstruction when situational, attentional and emotional influences are held constant via random presentation of different intensities of externally applied airflow obstruction. Adolescents with stable asthma and normal controls (n=25+25) with lung functions of approximately 3.5 l forced expiratory volume in 1 s (FEV₁) breathed through a device which obstructed airflow with five stimulus intensities, analogous to a mean reduction in FEV₁ of 8–66%. A session consisted of 10 blocks, each with presentation of five stimulus intensities plus the baseline resistance of the apparatus. Breathlessness was continuously reported by moving a lever along a 10-point scale. The mean breathlessness was computed per stimulus intensity. Lung function and anxiety were measured before and after the test.

Participants with asthma, not controls, manifested a paradoxical response: they reported significantly more breathlessness, but undifferentially. One patient against 12 controls reported consistently more breathlessness from baseline to severe obstruction. The hypothesis was only supported for controls. Breathlessness did not correlate with severity of asthma, lung function, duration of asthma, number of exacerbations over the last six months, age, sex or anxiety.

It was concluded that the meaning of airflow obstruction in patients with asthma has changed and underlies their paradoxical responses, even when situational, attentional and emotional factors are controlled.     

Ratings of emotion in laterally presented faces: sex and handedness effects

Sixteen right-handed participants (8 male and 8 female students) and 16 left-handed participants (8 male and 8 female students) were presented with cartoon faces expressing emotions ranging from extremely positive to extremely negative. A forced-choice paradigm was used in which the participants were asked to rate the faces as either positive or negative. Compared to men, women rated faces more positively, especially in response to right visual field presentations. Women rated neutral and mildly positive faces more positively in the right than in the left visual field, whereas men rated these faces consistently across visual fields. Handedness did not affect the ratings of emotion. The data suggest a positive emotional bias of the left hemisphere in women.     

The variability of practice hypothesis in motor learning: does it apply to Alzheimer's disease?

Based on Schmidt's (1975) variability of practice hypothesis, this study examined acquisition and transfer of a gross motor skill, namely tossing, in 58 patients with Alzheimer's disease (AD) and 58 healthy older adults under constant, blocked, and random practice conditions. While healthy older adults were able to learn the tossing task equally well under the three practice conditions, only AD patients receiving constant practice showed significant improvements. Tests of intermediate transfer yielded the expected random practice advantage in healthy controls but not AD patients. None of the practice conditions facilitated intermediate transfer in AD patients; however, constant practice did benefit these impaired individuals on tests of near transfer. These results indicate that the variability of practice hypothesis does not extend to AD patients. As motor learning and transfer were clearly a function of constant practice, future attempts to retrain basic activities of daily living in AD patients should emphasize consistency in training.     

Renatus renatus: the Cartesian tradition in British neuroscience and the neurophilosophy of John Carew Eccles

J. C. Eccles (1903-1997) had a highly distinguished career in neurophysiology, being awarded the Nobel Prize for Medicine or Physiology in 1963. This paper sets him within the Cartesian tradition of British neurophysiology initiated by Thomas Henry Huxley in the mid-19th century. It shows how the mind-brain problematique of the Cartesian tradition troubled him throughout his career, leading him finally to a solution in terms of quantum microphysics and microphysiology. This position, which has subsequently become fashionable, is discussed and shown (at least in the form Eccles espoused) to provide no solution to the problem posed by Descartes in the early 17th century.     

A Note on (K)Nots: Response to Robert W. Kentridge''s Commentary

GY, an extensively studied human hemianope, is aware of salient visual events in his cortically blind field but does not call this "vision." To learn whether he has low-level conscious visual sensations or whether instead he has gained conscious knowledge about, or access to, visual information that does not produce a conscious phenomenal sensation, we attempted to image process a stimulus s presented to the impaired field so that when the transformed stimulus T(s) was presented to the normal hemifield it would cause a sensation similar to that caused by s in the impaired field. While degradation of contrast, spatio-temporal filtering, contrast reversal, and addition of smear and random blobs all failed to match the response to a flashed bar s(f), moving textures of low contrast were accepted to match the response to a moving contrast-defined bar, s(m). Orientation and motion direction discrimination of the perceptually matched stimuli [s(m) and T(s(m))] was closely similar. We suggest that the existence of a satisfactory match indicates that GY has phenomenal vision.     

Complementarity of Linguistic and Prosodic Processes in the Intact Brain

Despite considerable speculation in the research literature regarding the complementarity of functional lateralization of prosodic and linguistic processes in the normal intact brain, few studies have directly addressed this issue. In the present study, behavioral laterality indices of emotional prosodic and traditional linguistic speech functions were obtained for a sample of healthy young adults, using the dichotic listening method. After screening for adequate emotional prosody and linguistic recognition abilities, participants completed the Fused Rhymed Words Test (FRWT; Wexler & Halwes, 1983) and the Dichotic Emotion Recognition Test (DERT; McNeely & Netley, 1998). Examination of the difference in ear asymmetries for these measures within individuals revealed a complementary pattern in 78% of the sample. However, the correlation between laterality quotients for the FRWT and DERT was near zero, supporting Bryden's model of "statistical" complementarity (e.g., Bryden, 1990).