Graziano, M. S. A., Gross, C. G., Taylor, C. S. R., & Moore, T. (2004).
Multisensory neurons for the control of defensive movements. In
G. Calvert, C. Spence, & B. Stein (Ed.),
The Handbook of Multisensory Processes (pp. 443-452) . MIT Press.
Abstract
If a hornet flies toward your face, you might duck, squint, and lift your hand to block it. If the insect touches your hand, you might withdraw your hand, even pulling it behind your back. These defensive movements have a reflexive quality. They are fast and can occur without conscious planning or thought. They are similar in all people (see Figure 1). However, although they seem reflexive, defensive movements are also highly sophisticated. They can be elicited by touch, sight or sound. They involve coordination between different body parts, such as the arm and head. They are spatially specific: the body parts that move and the direction of movement are appropriate for the location of the threat. The movements can be stronger or weaker depending on external context or the internal state of the person. For example, someone whose “nerves are on edge” may give an exaggerated alerting response to an unexpected stimulus. What sensory-motor pathways in the brain coordinate this rich and complex behavior? We suggest that a special set of interconnected areas in the monkey brain monitors the location and movement of objects near the body and controls startle, flinch and defensive responses. This hypothesized “defensive” system, shown in Figure 2, includes the ventral intraparietal area (VIP), parietal area 7b, the polysensory zone (PZ) in the precentral gyrus, and the putamen. These brain areas are monosynaptically interconnected (Cavada and Goldman-Rakic 1989a,b; Cavada and Goldman-Rakic 1991; Kunzle 1978; Matelli et al. 1986; Mesulam et al. 1977; Parthasarathy et al. 1992; Weber and Yin 1984; Luppino et al., 1999). Of the four areas, PZ is closest to the motor output, sending direct projections to the spinal cord (Dum and Strick 1991). Electrical stimulation of PZ evokes defensive movements, such as withdrawal of the hand, squinting and turning of the head, ducking, or lifting the hand as if to defend the side of the head (Graziano, Taylor and Moore 2002).
PDF Graziano, M. S. A., Gross, C. G., Taylor, C. S. R., & Moore, T. (2004).
A system of multimodal areas in the primate brain. In
C. Spence & J. Driver (Ed.),
Crossmodal Space and Crossmodal Attention (pp. 51-67) . Oxford University Press.
AbstractIn this chapter, we suggest that a set of interconnected areas in the primate brain monitors the location and movement of objects near the body and controls startle, flinch and defensive responses. This hypothesized “defensive” system, shown in Fig. 1 in a side view of the monkey brain, includes the ventral intraparietal area (VIP), parietal area 7b, the polysensory zone (PZ) in the precentral gyrus, and the putamen. These brain areas are monosynaptically interconnected (Cavada & Goldman-Rakic, 1989a,b; Cavada & Goldman-Rakic, 1991; Matelli et al., 1986; Mesulam et al., 1977; Parthasarathy et al., 1992; Weber & Yin, 1984). Of the four areas, PZ is closest to the motor output, sending direct projections to the spinal cord (Dum & Strick, 1991).
PDF Graziano, M. S. A., Cooke, D. F., Taylor, C. S. R., & Moore, T. (2004).
Distribution of hand location in monkeys during spontaneous behavior.
Experimental Brain Research ,
155 (1), 30-36.
Publisher's VersionAbstractRecently it was shown that electrical stimulation of the precentral gyrus of monkeys can evoke complex, coordinated movements. In the forelimb representation, stimulation of each site caused the arm to move to a specific final posture, and thus the hand to move to a location in space. Among these stimulation-evoked hand locations, certain regions of the hand's workspace were more represented than others. We hypothesized that a similar non-uniform distribution of hand location should be present during a monkey's spontaneous behavior. The present study examined the distribution of hand location of monkeys in their home cages. This distribution was similar to that found by stimulation of the precentral gyrus. That is, arm postures that were over-represented in spontaneous behavior were also over-represented in the movements evoked by cortical stimulation.
PDF Graziano, M. S. A., Patel, K. T., & Taylor, C. S. R. (2004).
Mapping from motor cortex to biceps and triceps altered by elbow angle.
Journal of Neurophysiology ,
92 (1), 395-407.
Publisher's VersionAbstractThis experiment used cortical microstimulation to probe the mapping from primary motor cortex to the biceps and triceps muscles of the arm in monkeys. The mapping appeared to change depending on the angle at which the elbow was fixed. For sites in the dorsal part of the arm and hand representation, the effects of stimulation were consistent with initiating a movement of the elbow to an extended angle. Stimulation evoked more triceps activity than biceps activity, and this difference was largest when the elbow was fixed in a flexed angle. For sites in the ventral part of the arm and hand representation, stimulation had the opposite effect, consistent with initiating a movement of the elbow to a flexed angle. For these sites, stimulation evoked more biceps activity than triceps activity, and the difference was largest when the elbow was fixed in an extended angle. For sites located in intermediate positions, stimulation evoked an intermediate effect consistent with initiating a movement of the elbow to a middle, partially flexed angle. For these sites, when the elbow was fixed at a flexed angle, the evoked activity was largest in the triceps, and when the elbow was fixed at an extended angle, the evoked activity was largest in the biceps. These effects were obtained with 400-ms-long trains of biphasic pulses presented at 200 Hz and 30 microA. They were also obtained by averaging the effects of individual, 30-microA pulses presented at 15 Hz. How this stimulation-evoked topography relates to the normal function of motor cortex is not yet clear. One hypothesis is that these results reflect a cortical map of desired joint angle.
PDF Cooke, D. F., & Graziano, M. S. A. (2004).
Sensorimotor integration in the precentral gyrus: polysensory neurons and defensive movements.
Journal of Neurophysiology ,
91 (4), 1648-1660.
Publisher's VersionAbstractThe precentral gyrus of monkeys contains a polysensory zone in which the neurons respond to tactile, visual, and sometimes auditory stimuli. The tactile receptive fields of the polysensory neurons are usually on the face, arms, or upper torso, and the visual and auditory receptive fields are usually confined to the space near the tactile receptive fields, within about 30 cm of the body. Electrical stimulation of this polysensory zone, even in anesthetized animals, evokes a specific set of movements. The movements resemble those typically used to defend the body from objects that are near, approaching, or touching the skin. In the present study, to determine whether the stimulation-evoked movements represent a normal set of defensive movements, we tested whether they include a distinctive, nonsaccadic, centering movement of the eyes that occurs during defensive reactions. We report that this centering movement of the eyes is evoked by stimulation of sites in the polysensory zone. We also recorded the activity of neurons in the polysensory zone while the monkey made defensive reactions to an air puff on the face. The neurons became active during the defensive movement, and the magnitude of this activity was correlated with the magnitude of the defensive reaction. These results support the hypothesis that the polysensory zone in the precentral gyrus contributes to the control of defensive movements. More generally, the results support the view that the precentral gyrus can control movement at the level of complex sensorimotor tasks.
PDF Cooke, D. F., & Graziano, M. S. A. (2004).
Super-flinchers and nerves of steel: defensive movements altered by chemical manipulation of a cortical motor area.
Neuron ,
43 (4), 585-593.
Publisher's VersionAbstractIn a restricted zone of the monkey motor cortex, neurons respond to objects near, approaching, or touching the body. This polysensory zone was hypothesized to play a role in monitoring nearby stimuli for the guidance of defensive movements. To test this hypothesis, we chemically manipulated sites within that zone by injecting bicuculline (increasing neuronal activity) or muscimol (decreasing neuronal activity). Bicuculline caused the monkey to react in an exaggerated fashion to an air puff on the face and to objects approaching the face, whereas muscimol caused the monkey to react in a reduced fashion. The effects were expressed partly as a motor abnormality (affecting movement of the musculature contralateral to the injection site) but also partly as a sensory enhancement or sensory neglect (affecting responses to stimuli contralateral to the injection site). These findings suggest that the polysensory zone contributes to the ethologically important function of defense of the body.
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