Spatial extent of the local field potential in macaque area LIP
The spatial extent of gamma oscillations in the local field potential (LFP) is heavily debated at present. To address this issue we recorded multi-unit activity (MUA) and LFPs in the Lateral Intraparietal area (LIP) with a multi-electrode probe with 16 contact points spaced 150 microns apart (total distance covered: 2.25 mm). The recording cylinder was positioned in an oblique angel to allow recordings orthogonal to the lateral bank of the intraparietal sulcus. We positioned the probe so that all electrodes were located in the cortex of the lateral bank. Spike rate and LFP-activity were recorded while the monkey was performing a memory guided saccade task towards ten different positions in the contralateral visual field. We recorded activity in 14 grid positions, during 40 recording sessions. We found that only the MUA and high-gamma (80-170 Hz) power were significantly affected by target position. Furthermore, for every recording session, we determined the electrode which showed the highest visual spike rate response across target positions (0-320 ms after target onset), which we termed the primary electrode. We then calculated the MUA and LFP responses for this condition on neighboring electrodes and determined the distance from the primary electrode where the response fell below 50% of the response at the primary electrode. Consistent with previous studies we found that the visual MUA response was highly localized within 200 micron around the primary electrode: the MUA response fell below 50% of the primary electrode response at an average distance of 213 micron. The high-gamma response was also significantly affected by distance from the primary electrode but fell to 50% of the primary electrode response at an average distance of 1650 micron (where no MUA response was present), indicating that even the high-gamma oscillations are shared over a much larger distance across the cortical thickness. The medium gamma (50-80 Hz), low gamma (25-50 Hz), beta (12-25 Hz) and alpha (8-12 Hz) power never fell below 50% of the primary electrode response along the probe shaft. These results show that target-selective MUA responses in area LIP are highly localized, whereas LFP-responses, even in the high, medium and low gamma band, extend over a much larger region of cortex, sometimes even across the entire cortical thickness.
Acknowledgements
ERC-StG 260607, FWO, GOA, PFV, IUAP
Keywords:
multielectrode arrays,
Macaca mulatta,
Lateral Intraprietal Area (LIP),
Saccades,
local field potential (LFP)
Conference:
Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012.
Presentation Type:
Poster Presentation
Topic:
Other basic/clinical neurosciences topic
Citation:
Premereur
E and
Janssen
P
(2012). Spatial extent of the local field potential in macaque area LIP.
Conference Abstract:
Belgian Brain Council.
doi: 10.3389/conf.fnhum.2012.210.00072
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Received:
27 Aug 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Prof. Peter Janssen, KULeuven, Leuven, Belgium, Peter.Janssen@med.kuleuven.be