Human perceptual decision making: disentangling task onset and stimulus onset.

in Human brain mapping (2014), 35(7), 3170-87

The left dorsolateral prefrontal cortex (ldlPFC) has been highlighted as a key actor in human perceptual decision-making (PDM): It is theorized to support decision-formation independently of stimulus type ... [more ▼]

The left dorsolateral prefrontal cortex (ldlPFC) has been highlighted as a key actor in human perceptual decision-making (PDM): It is theorized to support decision-formation independently of stimulus type or motor response. PDM studies however generally confound stimulus onset and task onset: when the to-be-recognized stimulus is presented, subjects know that a stimulus is shown and can set up processing resources-even when they do not know which stimulus is shown. We hypothesized that the ldlPFC might be involved in task preparation rather than decision-formation. To test this, we asked participants to report whether sequences of noisy images contained a face or a house within an experimental design that decorrelates stimulus and task onset. Decision-related processes should yield a sustained response during the task, whereas preparation-related areas should yield transient responses at its beginning. The results show that the brain activation pattern at task onset is strikingly similar to that observed in previous PDM studies. In particular, they contradict the idea that ldlPFC forms an abstract decision and suggest instead that its activation reflects preparation for the upcoming task. We further investigated the role of the fusiform face areas and parahippocampal place areas which are thought to be face and house detectors, respectively, that feed their signals to higher level decision areas. The response patterns within these areas suggest that this interpretation is unlikely and that the decisions about the presence of a face or a house in a noisy image might instead already be computed within these areas without requiring higher-order areas. [less ▲]

Action effect anticipation: neurophysiological basis and functional consequences.

in Neuroscience and Biobehavioral Reviews (2012), 36(2), 943-59

Voluntary actions are thought to be selected with respect to their intended goal. Converging data suggests that medial frontal cortex plays a crucial role in linking actions to their predicted effects ... [more ▼]

Voluntary actions are thought to be selected with respect to their intended goal. Converging data suggests that medial frontal cortex plays a crucial role in linking actions to their predicted effects. Recent neuroimaging data also suggests that during action selection, the brain pre-activities the representation of the predicted action effect. We review evidence of action effect prediction, both in terms of its neurophysiological basis as well as its functional consequences. By assuming that action preparation includes activation of the predicted sensory consequences of the action, we provide a mechanism to understand sensory attenuation and intentional binding. In this account, sensory attenuation results from more difficult discrimination between the observed action effect and the pre-activation of the predicted effect, as compared to when no (or incorrect) prediction is present. Similarly, a predicted action effect should also reach the threshold of awareness faster (intentional binding), if its perceptual representation is pre-activated. By comparing this potential mechanism to mental imagery and repetition suppression we propose a possible neural basis for the processing of predicted action effects. [less ▲]

Perceptual criterion and motor threshold: a signal detection analysis of the relationship between perception and action.

in Experimental brain research (2007), 182(2), 179-88

Although a large number of studies have demonstrated that a motor response to a visual stimulus is, at least to some extent, independent of the perceptual response, little effort has been spent on the ... [more ▼]

Although a large number of studies have demonstrated that a motor response to a visual stimulus is, at least to some extent, independent of the perceptual response, little effort has been spent on the investigation of the explicit characteristics of this independency. In the present experiment, observers were presented with an S1-S2 stimulus-pair, with S1 within the threshold range and with S2 highly suprathreshold. S2 was displayed either at the same location as S1 (masked condition), or some degree to the left or right of S1 (non-masked). Both the observers' sensitivity to S1 and simple RTs elicited by the stimulus pair were jointly assessed on a trial-by-trial basis. Response times decreased with increasing S1 contrast for perceptual Hits both when S1 was masked by S2 and when it was not, but for Misses only when S1 was masked, though to a lesser extent than for Hits. When RTs are collapsed across perceptual Hits and Misses for any given S1-contrast, they were independent of whether S1 was masked or not. The data indicate that the motor system has a fixed, high-energy threshold, whereas the perceptual system has a d'-dependent criterion that can either be higher or lower than the motor threshold-depending on the particular conditions. [less ▲]