Biomedical subjects

Patrick Haggard

Publications and source records attributed to Patrick Haggard.

59 records · Page 4Linked to original sources

PubMed2002

Vision modulates somatosensory cortical processing.

Over 150 years ago, E.H. Weber declared that experience showed that tactile acuity was not affected by viewing the stimulated body part. However, more recent investigations suggest that cross-modal links do exist between the senses. Viewing the stimulated body site improves performance on tactile discrimination and detection tasks and enhances tactile acuity. Here, we show that vision modulates somatosensory cortex activity, as measured by somatosensory event-related potentials (ERPs). This modulation is greatest when tactile stimulation is task relevant. Visual modulation is not present in the P50 component reflecting the primary afferent input to the cortex but appears in the subsequent N80 component, which has also been localized to SI, the primary somatosensory cortex. Furthermore, we replicate previous findings that noninformative vision improves spatial acuity. These results are consistent with a hypothesis that vision modulates cortical processing of tactile stimuli via back projections from multimodal cortical areas. Several neurophysiological studies suggest that primary and secondary somatosensory cortex (SI and SII, respectively) activity can be modulated by spatial and tactile attention and by visual cues. To our knowledge, this is the first demonstration of direct modulation of somatosensory cortex activity by a noninformative view of the stimulated body site with concomitant enhancement of tactile acuity in normal subjects.

Adult↗

PubMed2002

Voluntary action and conscious awareness.

Humans have the conscious experience of 'free will': we feel we can generate our actions, and thus affect our environment. Here we used the perceived time of intentional actions and of their sensory consequences as a means to study consciousness of action. These perceived times were attracted together in conscious awareness, so that subjects perceived voluntary movements as occurring later and their sensory consequences as occurring earlier than they actually did. Comparable involuntary movements caused by magnetic brain stimulation reversed this attraction effect. We conclude that the CNS applies a specific neural mechanism to produce intentional binding of actions and their effects in conscious awareness.

Adult↗

PubMed2002

rTMS to the supplementary motor area disrupts bimanual coordination.

Bimanual coordination tasks form an essential part of our behaviour. One brain region thought to be involved in bimanual coordination is the supplementary motor area (SMA). We used repetitive transcranial magnetic stimulation (rTMS) at 1 Hz for 5 min to create a temporary virtual lesion of the rostral portion of the human SMA immediately prior to performance of a goal-directed bimanual coordination task. In two control conditions, participants underwent sham stimulation or stimulation over the primary motor cortex (MI). The experimental task was to open a drawer with the left hand, catch a ball with the right hand, and reinsert the ball into the drawer through an aperture just big enough for the ball to pass through, again with the right hand. Hence, the actions of one hand depend upon the actions of the other. We calculated time intervals between the successive component actions of one hand (unimanual intervals) and actions of both hands (bimanual intervals) and analyzed these intervals separately. Interestingly, none of the unimanual intervals were affected by the rTMS, but the variability of a critical bimanual interval--the time between the left hand opening the drawer and the right hand starting to move to catch the ball--was increased by rTMS over the rostral parts of the SMA. No such effect was seen following rTMS over MI or after sham rTMS. Our results suggest that the rostral parts of the SMA play an important role in aspects of functional bimanual tasks, which involve tight temporal coordination between different motor actions of the two hands.

Adult↗

PubMed2001

Look and feel.

It is known that the CNS integrates proprioceptive and visual information to calculate limb position. Recent studies implicate an additional process, which might involve initial visual calibration of limb position, or gaze signals resulting from eye movements towards the felt position.

Journal Article↗

PubMed2001

The psychology of action.

Actions are part of the way that the mind controls the body. Two fundamental psychological questions about actions are 'Where do they come from?' and 'How does the mind produce them?' These may be called the 'internal generation problem' and the 'information expansion problem' respectively. The importance of these questions was appreciated at the birth of the British Psychological Society (BPS) a century ago, though the experimental methods to study them were lacking. This article falls into two halves. The first half discusses some of the major epochs in the psychology of action over the last 100 years; the second half outlines some currently prominent research questions, and considers their historical antecedents. Finally, I offer some speculations regarding where future contributions to the psychology of action will be most fruitful.

Journal Article↗