Navigation-associated medial parietal neurons in monkeys
- *Division of Applied System Neuroscience, Advanced Medical Research Center, Nihon University Graduate School of Medical Science, Ohyaguchi-Kamicho 30-1, Itabashi, Tokyo 173-8610, Japan;
- †Japan Society for the Promotion of Science, Kojimachi 5-3-1, Chiyoda, Tokyo 102-8471, Japan;
- ‡Laboratory for Anatomy and Physiology, Tokyo Seiei College, Nishi-Shinkoiwa 1-7-5, Katsushika, Tokyo 124-8530, Japan;
- §Department of Physiology and Biochemistry, Chiba University School of Nursing, Inohana 1-8-1, Chuo, Chiba 260-8672, Japan; and
- ¶Advanced Research Institute for the Sciences and Humanities (ARISH), Nihon University, Kudan-Kita 4-2-1, Chiyoda, Tokyo 102-0073, Japan
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Edited by Dale Purves, Duke University Medical Center, Durham, NC, and approved September 14, 2006 (received for review May 23, 2006)
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Fig. 1.Navigation task in a virtual environment. (a) Floor plan of virtual building used in present study. The black dots indicate CPs, and the lines connecting them indicate the routes. The monkeys were required to navigate from one of the SPs (shaded circles) to one of the goal rooms. When starting from either of the SPs, the initial direction was toward CP no. 3. (b) Time sequence of trial (route no. 3, from SP A to Goal III). Each box indicates the image projected on the screen. The image was projected stereoscopically. The number on the upper left side of each box indicates the temporal order (see also Movie 1).
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Fig. 2.Recording site. (Upper) Medial view of a monkey's brain. The area enclosed by the dashed line indicates the recording area. The recording site was reconstructed on magnetic resonance images of each monkey. (Lower) Recording sites of navigation (red, green, and black circles) and movement-selective (blue circles) neurons in monkeys nos. 1 (Left) and 2 (Right). Red and green circles indicate the recording sites of route- and location-selective navigation neurons, respectively. The data obtained from both hemispheres are superimposed on those obtained from the right hemisphere. cgs, cingulate sulcus; pos, parietooccipital sulcus; cc, corpus callosum; and cals, calcarine sulcus.
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Fig. 3.Examples of navigation neurons. (a) (Top) Neuronal activity on route no. 4. Each histogram and raster diagram were aligned at the onset of movement at each CP or SP (vertical dark-blue line). The color used to underline each raster diagram indicates the type of movement during that period: green, forward movement; red, left turn; and blue, right turn. This neuron became active when the monkey made a left turn (red underline) at CP no. 4. (Middle and Bottom) This neuron did not respond when the monkey made a left turn at the other locations (CP no. 1 on route no. 5 and CP no. 5 on route no. 4). (Right) Discharge rates during all movement periods. The blue bars indicate neuronal activity during the left turn period. The response at CP no. 4 on route no. 4 was significantly stronger than those at the other CPs (P <0.05). The selectivity and discrimination indices for this neuron were 1.00 and 0.72, respectively. Rt, route; L, left turn; and R, right turn. (b) An example of route-selective navigation neuron. (Top) Neuronal activity on route no. 2. Note that this neuron became active when the monkey made a forward movement (green underline) from CP no. 3 on route no. 2. (Middle) Responses during forward movement from CP no. 3 on route no. 3. (Bottom) Responses during forward movement from CP no. 3 on route no. 4. Note that this neuron did not respond when the monkey made the same movement at the same location on these two routes. (Right) Discharge rate during all movement periods when the monkey made a forward movement. The red bars indicate the response to the same movement at the same CPs. Note that this neuron showed the strongest response at CP no. 3 on route no. 2; the response was significantly stronger than at other CPs (P <0.05). The selectivity and discrimination indices for this neuron were 1.00 and 0.67, respectively.
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Fig. 4.Distribution of selectivity (a) and discrimination indices (b) of navigation (orange) and nonselective (cyan) neurons.
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Fig. 5.Results of muscimol injection experiments. Each graph indicates the performance of the monkey during each experimental session. Performances were evaluated every 30 min after muscimol injection. The data are shown for each route. (Inset) The injection site. Closed circles indicate the sites where the effects of the injection could be observed. Sites with the minus sign are those showing no effects. ∗∗, P < 0.01; ∗, P < 0.05; †, P < 0.1.
Footnotes
- ‖To whom correspondence should be addressed. E-mail: masato{at}med.nihon-u.ac.jp
- © 2006 by The National Academy of Sciences of the USA
