Biomedical subjects

Hanna Chainay

Publications and source records attributed to Hanna Chainay.

5 recordsLinked to original sources

PubMed2006

The role of the supplementary motor area (SMA) in word production.

The supplementary motor area (SMA) is a key structure for behavioral planning and execution. Recent research on motor control conducted with monkeys and humans has put to light an anatomical and functional distinction between pre-SMA and SMA-proper. According to this view, the pre-SMA would be involved in higher level processes while the SMA-proper would be more closely tied to motor output. We extended this general framework to the verbal domain, in order to investigate the role of the SMA in speech production. We conducted two speech production experiments with fMRI where we manipulated parameters such as familiarity, complexity or constraints on word selection. The results reveal a parcellation of the SMA into three distinct regions, according to their involvement in different aspects of word production. More specifically, following a rostrocaudal gradient, we observed differential activations related to lexical selection, linear sequence encoding and control of motor output. A parallel organization was observed in the dorsolateral frontal cortex. By refining its anatomical and functional parcellation, these results clarify the roles of the SMA in speech production.

Adult↗

PubMed2004

Foot, face and hand representation in the human supplementary motor area.

The ability to localize the limb representation in the supplementary motor area (SMA) would be useful in planning surgical ablation of medial frontal lobe tumours. We investigated the relationship between the anatomy of the SMA and the functional representation of fingers, toes, and lips using fMRI in healthy volunteers. There was a significant difference between the location of the different body parts in the SMA, with a rostro-caudal location of the face, hand and foot areas. Limb representation was located in an area spanning < 1 cm rostral and 1 cm caudal to the paracentral sulcus. These results support the somatotopic organization of the human SMA and suggest that the paracentral sulcus represents a landmark for body representation.

Adult↗

PubMed2004

Neglected attention in apparent spatial compression.

Halligan and Marshall [Cortex 27 (1991) 623] devised a new test to evaluate the hypothesis that in visual neglect, left space is systematically compressed rightwards. In the critical condition of the original study, rows of horizontally arranged numbers with a target arrow pointing to one of them from the opposite margin of the display were presented. When asked to verbally identify the number indicated by the arrow, a right brain-damaged patient with left neglect and hemianopia often indicated a number to the right of the target. The more the target was located on the left, the greater the response shift rightward, as if rightward compression were linearly proportional to the co-ordinates of Euclidian space. However, a possible alternative account could be that the patient's attention was attracted by the numbers located to the right of the target digit, thus biasing her responses toward numbers on the right. To explore this hypothesis, we asked normal participants and patients with right hemisphere lesions, with and without neglect or hemianopia, to mark on the margin of a sheet the approximate location indicated by an arrow situated on the opposite margin. In three different conditions, the arrow indicated either one of several numbers or lines in a row, or a blank location on the sheet margin. Only patients with left neglect, and especially those with associated hemianopia, deviated rightward, and then crucially only on those conditions where visible targets were present, consistent with the attentional bias account.

Adult↗

PubMed2003

Ideomotor and ideational apraxia in corticobasal degeneration: a case study.

Corticobasal degeneration (CBD) is a progressive disorder that can be characterised by asymmetrical akinetic rigidity, involuntary movements, cortical sensory loss, alien limb syndrome and asymmetrical apraxia (Gibb et al., 1989; Rinnie et al., 1994). Diagnosis of praxic disabilities is thought to be essential for distinguishing CBD, in its early stage, from other akinetic-rigid syndromes. However, the nature of apraxia in CBD, and the relations between ideomotor and ideational apraxia, are not well understood. For example, if there is an ideational deficit in a given patient, does this deficit occur independently of any ideomotor disorder, or are the two impairments linked in some manner? In the present paper we report a case study of a patient with apraxia due to CBD. We examine whether the disorder is confined to production tasks, or whether there is also a related deficit in recognising the correct actions performed with objects (an ideational deficit). We also evaluate whether a disorder found for action with single objects dissociates from the ability to link multiple actions into more complex, everyday tasks. The performance of our patient showed an impairment in both action production and action recognition system, suggesting a component of ideational as well as ideomotor apraxia in CBD.

Apraxia, Ideomotor↗

PubMed2002

Privileged access to action for objects relative to words.

We compared action (pour or twist?) and contextual/semantic (found in kitchen?) decisions made to pictures of objects, nonobjects, and words. Although there was no advantage for objects over words in contextual/semantic decisions, there was an advantage for objects over words and nonobjects in action decisions. For objects, both action and contextual/semantic decisions were faster than naming; for words, the opposite occurred. These results extend the early results of Potter and Faulconer (1975) that there is privileged access to semantic memory for objects relative to that for words and privileged access to phonology for words. Our data suggest that, for objects, there is privileged access to action knowledge rather than to all forms of semantic knowledge and that this is contingent on learned associations between objects and actions.

Association Learning↗