Biomedical subjects

A S Cauquil

Publications and source records attributed to A S Cauquil.

4 recordsLinked to original sources

PubMed2000

Is the face-sensitive N170 the only ERP not affected by selective attention?

We assessed the effect of directed attention on early neurophysiological indices of face processing, measuring the N170 event-related potential (ERP). Twelve subjects were tested on two tasks each in which they attended either to eyes only or to faces with eyes closed, presented within series of facial and control stimuli. Consistent with the ERP literature, N170 was recorded to facial stimuli at posterior temporal electrodes and a concomitant positive peak at the vertex, with latencies around 150 ms for faces and 174 ms for eyes. However, unlike fMRI studies, neither the latency nor the amplitude of the peaks were sensitive to the target/non-target status of either the eyes or the face stimuli. This suggests that early stages of face processing indexed by N 170 are automatic and unmodified by selective attention.

Adult↗

PubMed1999

Static and dynamic balance function in spasmodic torticollis.

The consequences of abnormal head posture on static and dynamic balance skill were studied in a group of 10 patients with idiopathic spasmodic torticollis (ST). In static conditions, body sway was assessed using a conventional force platform with eyes open and with eyes closed. Standardized dynamic balance conditions were produced using a rocking platform; lateral and anteroposterior dynamic balance skills were assessed by measuring linear displacement both of the body base and of the head. Dynamic tests were repeated 6 weeks after botulinum toxin treatment in all patients. Patients' results were compared with those obtained from 10 control subjects. In static conditions, ST patients did not differ from control subjects, but in dynamic conditions, balance parameters were greater in the patient group than in the control group. This was true for the lateral direction and for dynamic balance parameters recorded both before and after botulinum toxin treatment. Eye closure significantly increased dynamic balance parameters in both groups. However, the effect of eye closure was greater in the patient group than the control group, especially for lateral sway, suggesting that patients used vision to compensate for the dynamic balance disturbance induced by the spasmodic torticollis. Despite a significant improvement of head posture in all patients after botulinum toxin treatment, no significant changes in dynamic balance parameters were observed between the first and second test. The possible origins of the dynamic balance disturbance observed in ST patients are discussed.

Adult↗

PubMed1998

Galvanic vestibular stimulation modulates voluntary movement of the human upper body.

1. We have investigated whether vestibular information plays a role in the control of voluntary movement of the upper body. Movement consisted of a lateral tilt of the upper body in the frontal plane through an angle of about 8 deg. The influence of vestibular input was assessed from the effect of long duration (3-6 s), low-intensity (0.7 mA) galvanic vestibular stimulation (GVS) applied at different times relative to the movement. 2. GVS always produced a tilt of the body in the frontal plane but the response was larger and more prolonged when the onset of stimulation coincided with the cue to start moving compared with when it was applied some seconds after movement onset (i.e. while the subject was stationary in a tilted posture). 3. When the stimulus began 2 s before the voluntary movement the response consisted of two distinct components separated in time, one that was linked to the onset of GVS and another that was linked to onset of the voluntary movement. The large response observed when GVS onset coincided with the movement cue resembled the sum (after realignment in time) of these two separate components. 4. We suggest that these two components of the response to GVS relate to two different uses of vestibular information for whole-body control: first, to help maintain balance of the body, and second, to help guide and improve the accuracy of voluntary movements involving motion of the head in space.

Adult↗

PubMed1998

Lateral dynamic balance reactions to circular translation of the visual field.

Lateral sway of subjects in spontaneous dynamic balance conditions on a seesaw platform was measured during a visual stimulation monocularly produced by a rotating glass covered with a prism membrane. Prism rotation induced the perception of a circular translation of the whole visual field and an ocular pursuit movement. Therefore, the retinal slip that occurs in normal pursuit was cancelled. Strong stereotyped postural reactions were observed in a direction that depended upon both the vertical visual field deviation and the eye stimulated: upper position of the right visual field induced a leftward sway resulting from an extension of the right hemibody; symmetrical reactions occurred for the left stimulation. The results suggest that the postural reactions recorded depend on the isolated oculomotor activity and, in addition, on retinal afferences corresponding to the temporal crescent of the stimulated side, which orientates the postural reaction on the homolateral lower limb muscles.

Eye Movements↗