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Reaching activity in parietal area V6A of macaque: eye influence on arm activity or retinocentric coding of reaching movements?

Marzocchi N, Breveglieri R, Galletti C, Fattori P - Eur. J. Neurosci. (2008)

Bottom Line: The present study was aimed to disentangle the gaze effect from the effect of reaching activity upon single V6A neurons.Comparison of neural discharge of the same cell during execution of foveated and non-foveated reaching movements, performed towards the same or different spatial locations, confirmed that in a part of V6A neurons reaching activity is coded retinocentrically.The majority of V6A reaching neurons use a system that encompasses both of these reference frames.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy.

ABSTRACT
Parietal area V6A contains neurons modulated by the direction of gaze as well as neurons able to code the direction of arm movement. The present study was aimed to disentangle the gaze effect from the effect of reaching activity upon single V6A neurons. To this purpose, we used a visuomotor task in which the direction of arm movement remained constant while the animal changed the direction of gaze. Gaze direction modulated reach-related activity in about two-thirds of tested neurons. In several cases, modulations were not due to the eye-position signal per se, the apparent eye-position modulation being just an epiphenomenon. The real modulating factor was the location of reaching target with respect to the point gazed by the animal, that is, the retinotopic coordinates towards which the action of reaching occurred. Comparison of neural discharge of the same cell during execution of foveated and non-foveated reaching movements, performed towards the same or different spatial locations, confirmed that in a part of V6A neurons reaching activity is coded retinocentrically. In other neurons, reaching activity is coded spatially, depending on the direction of reaching movement regardless of where the animal was looking at. The majority of V6A reaching neurons use a system that encompasses both of these reference frames. These results are in line with the view of a progressive visuomotor transformation in the dorsal visual stream, that changes the frame of reference from the retinocentric one, typically used by the visual system, to the arm-centred one, typically used by the motor system.

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V6A neuron spatially tuned during the execution of reaching movements in the foveal reaching task. Note that in this task the location of reaching target and that of fixation point were always spatially coincident. Scale bar in PSTHs: 85 spikes/s. Other details as in Fig. 2.
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fig09: V6A neuron spatially tuned during the execution of reaching movements in the foveal reaching task. Note that in this task the location of reaching target and that of fixation point were always spatially coincident. Scale bar in PSTHs: 85 spikes/s. Other details as in Fig. 2.

Mentions: Figure 9 shows an example of a cell modulated in the foveal reaching task, both in FIX and MOV in a consistent way. When the animal gazed and reached the target in the left part of the panel, cell activity was low both in FIX and MOV epochs. When the monkey gazed and reached out the target in the central part of the panel or rightwards, both FIX and MOV activities were higher. We found that about half of tested neurons were sensitive to the direction of movement or the position of arm in space, in agreement with a previous report (Fattori et al., 2005). In particular, 31 out of 54 neurons (57%) showed a significant modulation in MOV, and 31 out of 54 (57%) in HOLD (anova, P < 0.05).


Reaching activity in parietal area V6A of macaque: eye influence on arm activity or retinocentric coding of reaching movements?

Marzocchi N, Breveglieri R, Galletti C, Fattori P - Eur. J. Neurosci. (2008)

V6A neuron spatially tuned during the execution of reaching movements in the foveal reaching task. Note that in this task the location of reaching target and that of fixation point were always spatially coincident. Scale bar in PSTHs: 85 spikes/s. Other details as in Fig. 2.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2268963&req=5

fig09: V6A neuron spatially tuned during the execution of reaching movements in the foveal reaching task. Note that in this task the location of reaching target and that of fixation point were always spatially coincident. Scale bar in PSTHs: 85 spikes/s. Other details as in Fig. 2.
Mentions: Figure 9 shows an example of a cell modulated in the foveal reaching task, both in FIX and MOV in a consistent way. When the animal gazed and reached the target in the left part of the panel, cell activity was low both in FIX and MOV epochs. When the monkey gazed and reached out the target in the central part of the panel or rightwards, both FIX and MOV activities were higher. We found that about half of tested neurons were sensitive to the direction of movement or the position of arm in space, in agreement with a previous report (Fattori et al., 2005). In particular, 31 out of 54 neurons (57%) showed a significant modulation in MOV, and 31 out of 54 (57%) in HOLD (anova, P < 0.05).

Bottom Line: The present study was aimed to disentangle the gaze effect from the effect of reaching activity upon single V6A neurons.Comparison of neural discharge of the same cell during execution of foveated and non-foveated reaching movements, performed towards the same or different spatial locations, confirmed that in a part of V6A neurons reaching activity is coded retinocentrically.The majority of V6A reaching neurons use a system that encompasses both of these reference frames.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy.

ABSTRACT
Parietal area V6A contains neurons modulated by the direction of gaze as well as neurons able to code the direction of arm movement. The present study was aimed to disentangle the gaze effect from the effect of reaching activity upon single V6A neurons. To this purpose, we used a visuomotor task in which the direction of arm movement remained constant while the animal changed the direction of gaze. Gaze direction modulated reach-related activity in about two-thirds of tested neurons. In several cases, modulations were not due to the eye-position signal per se, the apparent eye-position modulation being just an epiphenomenon. The real modulating factor was the location of reaching target with respect to the point gazed by the animal, that is, the retinotopic coordinates towards which the action of reaching occurred. Comparison of neural discharge of the same cell during execution of foveated and non-foveated reaching movements, performed towards the same or different spatial locations, confirmed that in a part of V6A neurons reaching activity is coded retinocentrically. In other neurons, reaching activity is coded spatially, depending on the direction of reaching movement regardless of where the animal was looking at. The majority of V6A reaching neurons use a system that encompasses both of these reference frames. These results are in line with the view of a progressive visuomotor transformation in the dorsal visual stream, that changes the frame of reference from the retinocentric one, typically used by the visual system, to the arm-centred one, typically used by the motor system.

Show MeSH
Related in: MedlinePlus