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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: J Neural Eng. 2013 Oct 25;10(6):066011. doi: 10.1088/1741-2560/10/6/066011

Figure 2. Microstimulation of the thalamus produces a nonlinear cortical response.

Figure 2

(a) Top: By averaging within a single cortical column, we obtain a timecourse of cortical activation with high signal to noise ratio. The “tick” represents the presentation time of the stimulus, which is a symmetric biphasic current waveform. The height of the “ticks” throughout the paper indicates the current amplitude of the stimulus. Microstimulation elicited a characteristic timecourse in the cortical response (single trials in gray, trial-averaged response in black). Bottom: When normalized by the amplitude of the response, the timecourse was consistent across a wide range of stimulus intensities and response amplitudes. (b) The amplitude of the cortical response displayed a nonlinear relationship with the current intensity of the single electrical stimulus. The currents used in (a) are color-coded in (b) for reference. (c) Microstimulation of the thalamus engaged two sets of nonlinear dynamics. A strong electrical stimulus suppressed the response to a second electrical stimulus, with the suppression decreasing for long inter-stimulus intervals. A weak electrical stimulus, however, caused profound facilitation of the response to the second stimulus. This facilitation principally occurs for inter-stimulus intervals of 100–200 milliseconds.