Constraint-induced movement therapy (CI), a standardized intensive rehabilitation intervention, was given to patients a year or more following stroke. The goal was to determine if CI was more effective than a less-intensive control intervention in changing motor function and/or brain physiology and to gain insight into the mechanisms underlying this recovery process. Subjects were recruited and randomized more than 1 year after a single subcortical infarction. Clinical assessments performed before and after the intervention and at 6 months postintervention included the Wolf Motor Function Test (WMFT), the Motor Activity Log (MAL), and the Assessment of Motor and Process Skills (AMPS). Transcranial magnetic stimulation was used to map the motor cortex. Positron emission tomography was used to measure changes in motor task-related activation due to the intervention. MAL increased by 1.08 after CI therapy and decreased by 0.01 after control therapy. The difference between groups was significant (P < 0.001). Changes in WMFT and AMPS were not significantly different between groups. Cerebral activation during a motor task decreased significantly, and motor map size increased in the affected hemisphere motor cortex in CI patients but not in control patients. Both changes may reflect improved ability of upper motor neurons to produce movement.

Intersensory temporal synchrony is an ubiquitous sensory attribute that has proven to be critical for binding multisensory inputs, sometimes erroneously leading to dramatic perceptual illusions. However, little is known about how the brain detects temporal synchrony between multimodal sensory inputs. We used positron emission tomography to demonstrate that detecting auditory-visual stimulus onset asynchrony activates a large-scale neural network of insular, posterior parietal, prefrontal, and cerebellar areas with the highest and task-specific activity localized to the right insula. Interregional covariance analysis further showed significant task-related functional interactions between the insula, the posterior thalamus, and superior colliculus. Based on these results and the available electrophysiological and anatomical connectivity data in animals, we propose that the insula, via its known short-latency connections with the tectal system, mediates temporally defined auditory-visual interaction at an early stage of cortical processing permitting phenomena such as the ventriloquist and the McGurk illusions.Key words: audiovisual asynchrony; temporal integration; insular cortex; PET; multisensory; cortical processing A fundamental brain function is to integrate information available to multiple sensory modalities producing a unified representation of the external world. Although multimodal sensory inputs from a single object or event normally coincide both in space and time, intersensory integration mechanisms seem to rely more critically on their temporal than spatial congruence (e.g., the ventriloquist effect) (Bertelson and Radeau, 1981). Indeed, the ability to detect and use temporal synchrony in associating multimodal sensory stimuli (e.g., sounds and visual events) has been demonstrated in human infants as young as 2 months (Lewkowicz, 1996(Lewkowicz, , 2000, and is believed to be operational at birth providing an innate capacity on which intermodal perception and associative learning are based (Spelke, 1987;Bahrick, 1992). Yet, the neural correlates for this basic process remain unknown. Using positron emission tomography (PET), we studied normal human subjects while performing a task requiring detection of auditory-visual stimulus onset asynchrony as well as a matched control condition. The PET experiment was designed for both paired image subtraction and correlational analysis methods. Brain regions specifically involved in temporal synchrony-asynchrony detection process were postulated where regional cerebral blood flow (rCBF) responses during task performance are significantly higher than during the control condition and appropriately modulated as a function of increasing task demand. MATERIALS AND METHODSSubjects. T welve right-handed healthy volunteers (seven men, five women, ages 27-56 years) participated in behavioral and PET experiments after giving written informed consent.Behavioral task s. Subjects' ability to detect intermodal temporal mismatch between simple stationary auditory and visual st...

Although the importance of the posterior parietal and prefrontal regions in spatial localization of visual stimuli is well established, their role in auditory space perception is less clear. Using positron emission tomography (PET) during auditory and visual spatial localization in the same subjects, modality-specific areas were identified in the superior parietal lobule, middle temporal and lateral prefrontal cortices. These findings suggest that, similar to the visual system, the hierarchical organization of the auditory system extends beyond the temporal lobe to include areas in the posterior parietal and prefrontal regions specialized in auditory spatial processing. Our results may explain the dissociation of visual and auditory spatial localization deficits following lesions involving these regions.

Little is known about how the brain binds together signals from multiple sensory modalities to produce unified percepts of objects and events in the external world. Using event-related functional magnetic resonance imaging (fMRI) in humans, we measured transient brain responses to auditory/visual binding, as evidenced by a sound-induced change in visual motion perception. Identical auditory and visual stimuli were presented in all trials, but in some trials they were perceived to be bound together and in others they were perceived as unbound unimodal events. Cross-modal binding was associated with higher activity in multimodal areas, but lower activity in predominantly unimodal areas. This activation pattern suggests that a reciprocal and 'competitive' interaction between multimodal and unimodal areas underlies the perceptual interpretation of simultaneous signals from multiple sensory modalities.