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S38-1 Face perception: Overview
S56
Oral Presentations: Symposia
S37-6 Mirror movements
S38. Face perception
M. Cincotta1 Unit of Neurology, Florence Health Authority, Florence, Italy
S38-1 Face perception: Overview
In humans, execution of unimanual motor tasks requires a neural network that is capable of restricting motor output activity to the primary motor cortex (M1) contralateral to the voluntary movement. The motor command is transmitted from the M1 to the contralateral spinal motoneurons by a largely crossed system of fast-conducting corticospinal neurons. Alteration or even transient dysfunction of the neural circuits underlying movement lateralization may result in involuntary mirror movements (MM). Overt MM can be seen in healthy children up to ten years of age, likely due to immaturity of the motor system. In adulthood, the persistence or the reappearance of strong and sustained MM is considered abnormal, although a tendency for the movements of the upper extremities to be drawn towards one another is suggested by the subtle mirroring that can be present also in healthy adults during intended unilateral tasks. Over the last two decades, transcranial magnetic stimulation (TMS) proved as a valuable, non-invasive neurophysiological tool to investigate motor control in healthy volunteers and neurological patients. The various ways how TMS and surface EMG techniques have been used to investigate the different neural mechanisms underlying congenital and acquired MM will be discussed. The main data resulting from the application of these techniques can be summarized as follow. In persistent congenital MM, the neurophysiological hallmark is the presence of separate, fast-conducting corticospinal fibers connecting abnormally the hand area of the M1 with both sides of the spinal cord. In patients with persistent congenital MM not associated with severe hemispheric lesions, studies suggest in addition a contribution of abnormal activity in the voluntarily nonactivated M1 to the emergence of MM. Acquired MM associated with Parkinson’s disease do not depend on unmasking of ipsilateral projections but are explained by motor output along the crossed corticospinal projection from the mirror M1.
A. Puce1 1 Department of Psychological and Brain Sciences, Indiana University, USA
1
S37-7 Long-term effect of repetitive transcranial magnetic stimulation over the premotor cortex for upper limb dystonia
Face perception forms the cornerstone for our interactions with others. We need to know who someone is, or what they are feeling or thinking. The primate brain has evolved to process this important stimulus category quickly and efficiently. The earliest research in this area noted impairments in human facial recognition in neuropsychological lesion studies, and provided the input for Bruce and Young’s (1986) model of face perception. Single-studies in monkeys originally demonstrated that neurons can respond selectively to the (conspecific) face, and that these neurons are located in the inferior temporal cortex and superior temporal sulcus. Human invasive electrophysiological studies have demonstrated focal-field potentials to faces in the fusiform gyrus and lateral temporal cortex. Non-invasive human EEG and MEG studies have also demonstrated these selective neural responses to faces which typically occur within the first 500 ms post-stimulus. PET and fMRI studies in humans have shown selective activation to faces in fusiform gyrus and lateral temporal cortex. Taken together, the results of all these investigations have seeded a face processing model which involves a ventral occipito-temporal branch for processing face identity, and a lateral occipito-temporal branch which deals primarily with analysis of facial movements and gaze direction (Allison et al 2000; Hoffman & Haxby 2000). The most recent social cognition studies indicate that facial expressions can be processed unconsciously. Face perception skills develop rapidly, and newborn infants show a preference for viewing elementary face-like forms. The development of aberrant face perception, e.g. in autism, is an important area of study, as is that in acquired face perception deficits e.g. prosopagnosia. Today’s state-of-the-art face perception studies often use multimodal assessment methods. Each of the speakers in this symposium will tackle an outstanding question in face perception, and showcase the wealth of methods that are used to study this scientific issue.
N. Murase1 , R. Urushihara1 , Y. Hosono1 , R. Kaji1 Department of Neurology, School of Medicine, Tokushima University, Tokushima, Japan
S38-2 EEG/MEG
Objective: Approximately 30% of patients with upper limb dystonia are poor responders for ordinary treatments. Though an acute effect of repetitive transcranial magnetic stimulation (rTMS) over the premotor cortex was reported (Murase N et al., 2005), it is unclear whether rTMS is clinically applicable or not. This study was aimed to evaluate a longterm effect in chronic use of rTMS for upper limb dystonia. Methods: Ninety four patients with idiopathic upper limb dystonia who had a history of heavy use writing were enrolled. Twenty four patients among them were resistant to botulinum toxin, muscle afferent block and oral medications. rTMS over the premotor cortex was tried and 17 patients (71%) showed an acute effect. For those patients (7 female, mean age 37.7 years) rTMS was applied every two to four weeks for at least one year. For six patients, who were possible to be in hospital, rTMS was given twice a week at the beginning. 0.2 Hz, subthreshold rTMS over the premotor cortex (250 pulses per one trial) was used. Before each trial, clinical effect for one month was evaluated by BFM scale. Resting motor threshold, MEP amplitude, and silent period were also measured. This is a single-blind, and not a case-control study. Results: In regularly stimulated patients, BFM scale was improved after one year (before 3.8±1.6, after 2.2±1.9 (SD)). Silent period was increased significantly after 4 months but the change was saturated. In contrast, six patients, who were treated intensively at the beginning of rTMS induction, showed marked change of BFM scale (before 5.5±3.7, after 0.8±0.8) in one year. Silent period was prolonged only after one month. Conclusion: When rTMS was used repeatedly, initial intensive stimulation was important for the induction of long-term effect, probably through the mechanism of GABAgic synapses.
1
1
R. Kakigi1 Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan
We have been studying the underlying mechanisms of face perception in humans using magneto- (MEG) and electro-encephalography (EEG) including (1) the face inversion effect, (2) perception of eye motion, (3) perception of mouth motion, (4) effects of face contour and features on early occipitotemporal activity when viewing eye movement, and (5) subliminal effects on face perception. Latencies with inverted faces relative to those with upright faces were longer in the right hemisphere and shorter in the left hemisphere. Since the activated regions under upright and those under inverted face stimuli did not show a significant difference, we consider that differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions. When viewing the motion of the mouth and eyes, a large clear MEG component, 1M (mean peak latency of approximately 160 ms), was elicited to both mouth and eye movement, and was generated mainly in the occipitotemporal border, at human MT/V5. The 1M to mouth movement and the 1M to eye movement showed no significant difference in amplitude or generator location. Therefore, our results indicate that human MT/V5 is active in the perception of both mouth and eye motion, and that the perception of movement of facial parts is probably processed similarly. We found that the contour and facial features (lip), mainly the former, significantly enhanced MT/V5 activity when viewing eye movement, even if the physical factors of movement were the same for all the conditions. This result indicates whether the stimuli is face (eyes) or not is very important for visual perception for us. Even if the stimuli were subliminal (subthreshold), cortical activity by viewing face was significantly larger than viewing letter or star, indicating that face is recognized in special processing in human brain.
Oral Presentations: Symposia
S37-6 Mirror movements
S38. Face perception
M. Cincotta1 Unit of Neurology, Florence Health Authority, Florence, Italy
S38-1 Face perception: Overview
In humans, execution of unimanual motor tasks requires a neural network that is capable of restricting motor output activity to the primary motor cortex (M1) contralateral to the voluntary movement. The motor command is transmitted from the M1 to the contralateral spinal motoneurons by a largely crossed system of fast-conducting corticospinal neurons. Alteration or even transient dysfunction of the neural circuits underlying movement lateralization may result in involuntary mirror movements (MM). Overt MM can be seen in healthy children up to ten years of age, likely due to immaturity of the motor system. In adulthood, the persistence or the reappearance of strong and sustained MM is considered abnormal, although a tendency for the movements of the upper extremities to be drawn towards one another is suggested by the subtle mirroring that can be present also in healthy adults during intended unilateral tasks. Over the last two decades, transcranial magnetic stimulation (TMS) proved as a valuable, non-invasive neurophysiological tool to investigate motor control in healthy volunteers and neurological patients. The various ways how TMS and surface EMG techniques have been used to investigate the different neural mechanisms underlying congenital and acquired MM will be discussed. The main data resulting from the application of these techniques can be summarized as follow. In persistent congenital MM, the neurophysiological hallmark is the presence of separate, fast-conducting corticospinal fibers connecting abnormally the hand area of the M1 with both sides of the spinal cord. In patients with persistent congenital MM not associated with severe hemispheric lesions, studies suggest in addition a contribution of abnormal activity in the voluntarily nonactivated M1 to the emergence of MM. Acquired MM associated with Parkinson’s disease do not depend on unmasking of ipsilateral projections but are explained by motor output along the crossed corticospinal projection from the mirror M1.
A. Puce1 1 Department of Psychological and Brain Sciences, Indiana University, USA
1
S37-7 Long-term effect of repetitive transcranial magnetic stimulation over the premotor cortex for upper limb dystonia
Face perception forms the cornerstone for our interactions with others. We need to know who someone is, or what they are feeling or thinking. The primate brain has evolved to process this important stimulus category quickly and efficiently. The earliest research in this area noted impairments in human facial recognition in neuropsychological lesion studies, and provided the input for Bruce and Young’s (1986) model of face perception. Single-studies in monkeys originally demonstrated that neurons can respond selectively to the (conspecific) face, and that these neurons are located in the inferior temporal cortex and superior temporal sulcus. Human invasive electrophysiological studies have demonstrated focal-field potentials to faces in the fusiform gyrus and lateral temporal cortex. Non-invasive human EEG and MEG studies have also demonstrated these selective neural responses to faces which typically occur within the first 500 ms post-stimulus. PET and fMRI studies in humans have shown selective activation to faces in fusiform gyrus and lateral temporal cortex. Taken together, the results of all these investigations have seeded a face processing model which involves a ventral occipito-temporal branch for processing face identity, and a lateral occipito-temporal branch which deals primarily with analysis of facial movements and gaze direction (Allison et al 2000; Hoffman & Haxby 2000). The most recent social cognition studies indicate that facial expressions can be processed unconsciously. Face perception skills develop rapidly, and newborn infants show a preference for viewing elementary face-like forms. The development of aberrant face perception, e.g. in autism, is an important area of study, as is that in acquired face perception deficits e.g. prosopagnosia. Today’s state-of-the-art face perception studies often use multimodal assessment methods. Each of the speakers in this symposium will tackle an outstanding question in face perception, and showcase the wealth of methods that are used to study this scientific issue.
N. Murase1 , R. Urushihara1 , Y. Hosono1 , R. Kaji1 Department of Neurology, School of Medicine, Tokushima University, Tokushima, Japan
S38-2 EEG/MEG
Objective: Approximately 30% of patients with upper limb dystonia are poor responders for ordinary treatments. Though an acute effect of repetitive transcranial magnetic stimulation (rTMS) over the premotor cortex was reported (Murase N et al., 2005), it is unclear whether rTMS is clinically applicable or not. This study was aimed to evaluate a longterm effect in chronic use of rTMS for upper limb dystonia. Methods: Ninety four patients with idiopathic upper limb dystonia who had a history of heavy use writing were enrolled. Twenty four patients among them were resistant to botulinum toxin, muscle afferent block and oral medications. rTMS over the premotor cortex was tried and 17 patients (71%) showed an acute effect. For those patients (7 female, mean age 37.7 years) rTMS was applied every two to four weeks for at least one year. For six patients, who were possible to be in hospital, rTMS was given twice a week at the beginning. 0.2 Hz, subthreshold rTMS over the premotor cortex (250 pulses per one trial) was used. Before each trial, clinical effect for one month was evaluated by BFM scale. Resting motor threshold, MEP amplitude, and silent period were also measured. This is a single-blind, and not a case-control study. Results: In regularly stimulated patients, BFM scale was improved after one year (before 3.8±1.6, after 2.2±1.9 (SD)). Silent period was increased significantly after 4 months but the change was saturated. In contrast, six patients, who were treated intensively at the beginning of rTMS induction, showed marked change of BFM scale (before 5.5±3.7, after 0.8±0.8) in one year. Silent period was prolonged only after one month. Conclusion: When rTMS was used repeatedly, initial intensive stimulation was important for the induction of long-term effect, probably through the mechanism of GABAgic synapses.
1
1
R. Kakigi1 Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan
We have been studying the underlying mechanisms of face perception in humans using magneto- (MEG) and electro-encephalography (EEG) including (1) the face inversion effect, (2) perception of eye motion, (3) perception of mouth motion, (4) effects of face contour and features on early occipitotemporal activity when viewing eye movement, and (5) subliminal effects on face perception. Latencies with inverted faces relative to those with upright faces were longer in the right hemisphere and shorter in the left hemisphere. Since the activated regions under upright and those under inverted face stimuli did not show a significant difference, we consider that differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions. When viewing the motion of the mouth and eyes, a large clear MEG component, 1M (mean peak latency of approximately 160 ms), was elicited to both mouth and eye movement, and was generated mainly in the occipitotemporal border, at human MT/V5. The 1M to mouth movement and the 1M to eye movement showed no significant difference in amplitude or generator location. Therefore, our results indicate that human MT/V5 is active in the perception of both mouth and eye motion, and that the perception of movement of facial parts is probably processed similarly. We found that the contour and facial features (lip), mainly the former, significantly enhanced MT/V5 activity when viewing eye movement, even if the physical factors of movement were the same for all the conditions. This result indicates whether the stimuli is face (eyes) or not is very important for visual perception for us. Even if the stimuli were subliminal (subthreshold), cortical activity by viewing face was significantly larger than viewing letter or star, indicating that face is recognized in special processing in human brain.