Looking into Task-Specific Activation Using a Prosthesis Substituting Vision with Audition

Figure 3

fMRI paradigm (see Section 2). We show here the temporal course of a representative run with the representation of some stimuli used in the conditions with the SSD. L: localization task, O: orientation detection task and C: control task. Visual representations and corresponding spectrograms of representative stimuli are displayed in the lower part of the figure in order to illustrate the image-to-sound conversion. On the left, one pair for the experimental condition (localization or orientation), where the sounds correspond to a horizontal bar followed by a vertical bar presented both in the middle-lower part of the artificial retina). On the right, one pair for the control condition, where the sounds correspond to three isolated pixels presented in the SSD artificial retina. The spectrograms below each stimulus are the spectral frequency display (top) and the waveform display (bottom) of 400 msec extracts of the corresponding sounds. In each display, the 𝑥-axis (horizontal ruler) measures time (expressed in hms, in a time window of 900 msec, for display purposes). In the spectral frequency display, the 𝑦-axis (vertical ruler) measures frequency (expressed in Hz), low-amplitude audio frequencies are in dark color and high-amplitude frequencies are in bright color. In the waveform display, the 𝑦-axis (vertical ruler) measures amplitude (the loudness of the audio signal on a decibel scale that ranges from [−Infinity] to zero dBFS).