Modality-specific and modality-general mechanisms of perceptual decision making
Final Report Abstract
Perceptual decision making (PDM) has so far mostly been studied in a modality-specific manner using different sensory stimulus material and task structures. One important approach is the study of visual random dot motion (RDM) tasks in non-human primates. In these studies, subjects are asked to detect the direction of motion from stimuli (i.e. a cloud of moving dots) and typically indicate their decision through saccades toward the dominant motion direction. These studies suggest that sensory evidence of directional motion encoded in the middle temporal region (MT) is integrated by neural accumulators in regions associated with planning and preparation of saccades such as the lateral intraparietal cortex (LIP) or the frontal eye fields (FEF) until the decision is reached. Another prominent approach focusses on vibrotactile decisions. These studies usually use (delayed) match-to-comparison tasks (DMTC) in which subjects have to decide which of two successively presented tactile stimuli on the fingers has a higher flutter frequency. The response is typically given by hand movements or button presses. Neural recordings show that vibrotactile decisions are coded by difference signals in brain regions that are associated with the response modality (e.g. in premotor cortex areas). A central question is whether these differing results from animal studies, which are similarly found non-invasively in humans, can be integrated into a suggested overarching intentional framework of decision making, or if they are due to the different sensory modalities, paradigms, or response effectors. In two fMRI studies with multivariate pattern analysis (MVPA), we investigated this question in modified vibrotactile DMTC tasks. By introducing a rule in which the first stimulation is compared against the second or the second against the first, we were able to control for the sequence in the stimulation, and, by instructions (match/mismatch and colour cues for response target movement), for the motor activity associated with the decision. In the first study (N=27), it was revealed that perceptual decisions are encoded in effector-specific brain areas without the motor responses being pre-planned. In the second study (N=36), it was shown that these results are consistent across the tactile and visual modality, i.e. that they are neither influenced by the modality nor by an interaction of the modality with the effectors. Thus, these studies represent a first important step towards integrating the two influential frameworks of perceptual decision making and, interestingly, point to an effector-specific but action-independent coding of perceptual decisions.
Publications
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Response modality-dependent categorical choice representations for vibrotactile comparisons. NeuroImage, 226, 117592.
Wu, Yuan-hao; Velenosi, Lisa A. & Blankenburg, Felix
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Effector-specific neural representations of perceptual choices across different sensory domains. 11th MindBrainBody Symposium, Berlin
Esmeyer, M., Schmidt, T.T. & Blankenburg, F.
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Effector-specific neural representations of perceptual choices across different sensory domains. FENS Forum 24, Vienna
Marlon Esmeyer, Timo Torsten Schmidt & Felix Blankenburg
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Effector-dependent neural representations of perceptual decisions independent of motor actions and sensory modalities. Imaging Neuroscience, 3.
Esmeyer, Marlon F.; Schmidt, Timo T. & Blankenburg, Felix
