Skip to main content
. 2023 Dec 13;131(1):106–123. doi: 10.1152/jn.00086.2023

Figure 2.

Figure 2.

Top: thermography during cortical cooling. To examine the cooling profile of our chips, a cooling chip was placed over areas 2 and 5 M. A: the outline (dashed rectangle) of the PDMS base is larger than the cooling channel (solid outline on cortex). Thermal images from matching perspective depicting cortex temperature prior to (B), during (C), and after cooling (D). Inflow and outflow tubes are outlined in black. Cortical temperature throughout the three epochs was also measured by a microthermocouple (mtc) under the device. The very cold temperatures (dark blue) in C are the coolant in the inflow and outflow tubes, not the cortical surface below the chip. A temperature scale is shown to the right of D and the deactivation isotherm (19–21°C) is indicated by a white square, which is also highlighted as a white ring during cooling (C). The temperature scale shows the time course of the thermal data from 5 pixels marked by colored circles in C at increasing 0.75-mm intervals from the cooling chip. The timing of the 3 frames (B–D) is shown by vertical gray lines on the plot. Cortical temperatures were stable within 1–2 min of cooling. Bottom: temporal sequence of data collection for each intracortical microstimulation (ICMS) site tested during cooling. For each cooling chip, data were collected from up to six stimulation epochs marked by red and blue flags. Cooling chips were activated at separate times (bottom square wave traces) while temperature on the M1 surface was measured (middle traces). Before cooling of chip 1, Baseline Epoch (red flag at left) ICMS movements were recorded on video. Chip 1 (brown traces) was then activated, and ICMS movements were again video recorded during up to 3 cooling epochs (blue flags) 1, 3, and 5 min after the time when cortex reached 10°C. If movements were abolished at 1 or 3 min, subsequent cooling epochs were not performed. Chip 1 was then turned off and ICMS movements were video recorded during rewarm epochs (red flags at center) 1 and 5 min after cortex temperature warmed passively to 34°C. Excitation thresholds were measured during Baseline, Cool 5, Rewarm 1, and Rewarm 5 Epochs. In monkeys with a second cooling chip, this cycle was repeated with the chip 1, Rewarm 5 Epoch serving as the Baseline Epoch for chip 2 (green traces). PDMS, polydimethylsiloxane.