Disorders of higher visual function and hemi-spatial neglect

Tonal cues modulate line bisection performance: preliminary evidence for a new rehabilitation prospect?

The effect of the presentation of two different auditory pitches (high and low) on manual line-bisection performance was studied to investigate the relationship between space and magnitude representations underlying motor acts. Participants were asked to mark the midpoint of a given line with a pen while they were listening a pitch via headphones. In healthy participants, the effect of the presentation order (blocked or alternative way) of auditory stimuli was tested (Experiment 1). The results showed no biasing effect of pitch in blocked-order presentation, whereas the alternative presentation modulated the line-bisection. Lower pitch produced leftward or downward bisection biases whereas higher pitch produced rightward or upward biases, suggesting that visuomotor processing can be spatially modulated by irrelevant auditory cues. In Experiment 2, the effect of such alternative stimulations in line bisection in right brain damaged patients with a unilateral neglect and without a neglect was tested. Similar biasing effects caused by auditory cues were observed although the white noise presentation also affected the patient's performance. Additionally, the effect of pitch difference was larger for the neglect patient than for the no-neglect patient as well as for healthy participants. The neglect patient's bisection performance gradually improved during the experiment and was maintained even after 1 week. It is therefore, concluded that auditory cues, characterized by both the pitch difference and the dynamic alternation, influence spatial representations. The larger biasing effect seen in the neglect patient compared to the no-neglect patient and healthy participants suggests that auditory cues could modulate the direction of the attentional bias that is characteristic of neglect patients. Thus, the alternative presentation of auditory cues could be used as rehabilitation for neglect patients. The space-pitch associations are discussed in terms of a generalized magnitude system.

Construct and ecological validity of the Occupational Therapy Adult Perceptual Screening Test (OT-APST)

This paper reports on the construct validity (scale design and convergent validity) and ecological validity of the Occupational Therapy Adult Perceptual Screening Test (OT-APST). The performance of 208 participants following stroke on the OT-APST and a reference tool (either the Loewenstein Occupational Therapy Cognitive Assessment (LOTCA) or the LOTCA-Geriatric version (LOTCA-G)) was compared. The OT-APST performance of the stroke sample was compared with a healthy normative sample (n = 356). The relationship between the OT-APST performance and the Functional Independence Measure (FIM) score of the participants following stroke was also examined. Factor analysis and internal consistency results supported the scale design of the OT-APST. Significant correlations between the performance of the participants following stroke on the OT-APST and the reference tool supported the convergent validity of the OT-APST. The ability of the OT-APST to separate the two participant groups provided further evidence of its construct validity. Significant correlations between OT-APST and FIM scores supported the ecological validity of this tool. This study shows that the OT-APST is an ecologically valid tool with demonstrated construct validity in the assessment of visual perception.

The role of the dorsal stream for gesture production

Skilled gestures require the integrity of the neural networks involved in storage, retrieval, and execution of motor programs. Premotor cortex and/or parietal cortex lesions frequently produce deficits during performance of gestures, transitive more than intransitive. The dorsal stream links object information with object action, suggesting that mechanical knowledge of tool use is stored focally in the brain. Using event-related fMRI, we explored activity during instructed-delay transitive and intransitive hand gestures. The comparison between planning-preparation and execution of gestures demonstrated a temporal rostral to caudal gradient of activation in the ventral premotor cortex (PMv) and inferior to superior gradient of activation in the posterior parietal cortex (PPc). Comparison between transitive and intransitive gestures established a functional specificity within the dorsal stream for mechanical knowledge. Results demonstrate that not only PPc but also the PMv acts in the processing of sensorimotor information during gestures. This might be the substrate underlying selective deficits in ideomotor apraxia patients.

Neurodegenerative disease and the evolution of art: the effects of presumed corticobasal degeneration in a professional artist

Production of art is a complex process involving a combination of technical skill and a unique talent. Changes in artistic ability may accompany neurodegenerative disorders when they occur in an artist. The nature of these changes in the context of definable regional neuropathological disturbances may provide insight into the structural basis of the creative process. We describe a professional artist in whom presumed corticobasal degeneration (CBD) was associated with an alteration of his artistic judgement and production. Disinhibition, perseveration, and left hemispatial neglect, features of his cognitive profile were readily discernible in his work. The differences in his style are examined with respect to his main neuroanatomic abnormalities, namely right cerebral hemiatrophy as defined by magnetic resonance and single-photon emission computed tomography imaging. Cognitive deficits, including visuoconstructive and motor neglect, apathy, perseveration, and disinhibition as determined by neuropsychological testing, contributed to the dissolution of his artistic skills. Our case study adds to the growing literature on the effects of brain damage on artistic expression in the graphic arts.