Characteristics of the SR-evoked potentials in area 3a.

<p>(A) Percent responses evoked by DR and SR stimulations in area 3a. (B) Percent responses evoked by DR and SR stimulations in area 3b/1. (C) Amplitude of the DR- and SR-evoked potentials in area 3a. (D) Latency of the DR- and SR-evoked potentials in area 3a. Error bars in A–D indicated S.E. Asterisk in A–D indicates statistical significance at <i>P</i> < 0.05 using two-sample <i>t</i>-test.</p

Schematic drawing of experimental setting and surface map of the recording sites.

<p>(A) Stimulation of deep radial (DR) and superficial radial (SR) nerves. Three nerve cuffs were implanted: one on the radial nerve trunk (R) at the left forearm, one on the DR, representing primarily muscle afferent input, and one on the SR, representing primarily input from the skin. The DR and SR cuffs were used for electrical stimulation, and the R cuff was used for recording incoming volleys. The nerves were stimulated with biphasic constant-current pulses, 100 μs/phase, at twice the threshold (2T). The electrical stimulation-evoked field potential was recorded from the forearm region at the posterior bank of the CS of the right hemisphere. (B) Cortical surface map of the recording sites in each monkey. The electrode was inserted 8–15 mm at the anterior–posterior level. Gray lines indicate the approximate location of the CS on the cortical surface. Recording sites of the SR- or DR-evoked potentials are indicated by filled circles. Open circles indicate electrode insertions in which intracortical microstimulations were applied and no SEPs were recorded. Body parts activated at the lowest current of the microstimulation are indicated by capital letters. Values indicate the lowest microstimulation current (μA) evoking the movement. “n” indicates no effect up to 200 μA. A: anterior, P: posterior, M: medial, L: lateral.</p

Relationship between response latency and amplitude of the DR- and SR-evoked potentials.

<p>(A) Plots of the DR-evoked potentials against latency and amplitude. The 57 responses observed from 179 recording sites in monkey SO are shown. (B) Same as A, but for monkey TA. The 50 responses of 168 recording sites are shown. (C, D) Same as (A, B), but for the SR-evoked potentials. The 163 responses observed from 179 recording sites in monkey SO (C) and 87 responses observed from 168 recording sites in monkey TA (D) are shown.</p

Examples of DR- and SR-evoked potential distribution in area 3a.

<p>(A) Amplitude plots of the DR-evoked potentials at the anterior-posterior 10-mm level in monkey SO where the largest DR-evoked potential was observed in this animal. The circle size indicates the amplitude. A bar indicates no significant activation. (B) Latency plots of the DR-evoked potential indicated by colors. (C, D) same as (A, B), but for the SR-evoked potentials. (E–H) Same as A-D but for monkey TA. The data in A11 were from where the largest DR-evoked potential was observed in this monkey. The scale bar indicates 5 mm, separated by black and gray every 1 mm.</p

Representative examples of DR- and SR-evoked potentials.

<p>(A) An example of the DR- and SR-evoked potentials recorded at the bottom of the posterior part of CS. Averaged traces of 60 trials are shown at the time aligned with DR and SR stimulations. An asterisk indicates a detected response compared with the baseline activity. Blue dotted lines indicate one standard deviation from the baseline activity. (B) Same as (A) except for recording at the superficial part of the posterior part of CS. (C) Reconstructed trace of the electrode insertion in which the SEPs in A and B were recorded. (D) An example of the thionine-stained coronal section in monkey SO. White arrows indicate the approximate locations of the borders of areas 4, 3a, 3b, and 1. Colored arrows indicate the lesion marks. The scale bars in C and D indicate 5 mm, separated by black and gray every 1 mm. (E) Amplitude plots of the DR- and SR-evoked potentials. The potentials were recorded every 1 mm from the surface to the bottom of the posterior part of CS as shown in C. (F) Latency plots of the DR- and SR-evoked potentials. In C, E, and F, characters A and B indicate the recording depth of the SEPs represented in A and B, respectively.</p

Overlaying plots of the DR- and SR-evoked potentials for all recording sites.

<p>(A) Amplitude of the DR-evoked potentials for all recording sites in monkey SO. The circle size indicates the amplitude. A bar at each recording site indicates no significant response. (B) Latency plots of the DR-evoked potentials for all recording sites in monkey SO. The latency is indicated by colors. The scale bar indicates 5 mm, separated by black and gray every 1 mm. (C, D) Same as (A, B), but for the SR-evoked potentials. (E–H) Same as A–D, but for monkey TA. All SEPs from multiple anterior-posterior level were overplayed into one typical histology section in each monkey.</p