The 4th Annual Meeting of the Neurophilosophy of Free Will Consortium
How does the brain stop us from making mistakes?
Imagine writing an email when you are upset. As you reach toward your phone to click “send”, you realize sending it would be a mistake; you change your mind and stop yourself from clicking. Once we act, how can we change our mind? “Free will” is a topic of lively philosophical inquiry but has limited grounding in physical observations. In the first part of this talk, I will show results from a change-of-mind (CoM) paradigm in which rats mistakenly act and then decide to stop the in-progress action. In the task, head-fixed rats discriminate two stimuli by either running on a treadmill past a distance threshold (Go) or remaining immobile (NoGo). On CoM trials, rats mistakenly begin running to the NoGo stimulus but soon realize their mistake and chose to return to immobility before crossing the threshold. We found two anterior cingulate cortex (ACC) neuronal ensembles for monitoring and adjusting actions that are distinguished by their operational timeframe. One performs real-time action monitoring to enact CoM, while the other looks back in time to monitor recent actions and outcomes. In the second part of the talk, I will discuss the neural causes of mistaken actions. Distinct groups of ACC neurons selectively respond, either to the Go, or the NoGo stimulus. On CoM trials, Go stimulus-preferring units aberrantly responded to the NoGo stimulus. If this stimulus-evoked response was larger, then the rat mistakenly ran faster. Thus, ignition of the wrong pool of stimulus-responsive neurons may drive mistaken actions. Finally, I will show that motor cortex EEG beta oscillations cause action stopping during a CoM and highlight their utility for controlling brain-machine interfaces.
The role of prestimulus and stimulus-elicited neural activity in eliciting conscious visual perception and moral responsibility
Prominent theoretical views have debated the role of consciousness in eliciting moral responsibility. One view holds that although an agent can be responsible for actions and outcomes that are affected by unconscious perceptions, they could be even more responsible if they were conscious of the relevant information. Empirical evidence has likewise shown that participants assigned higher responsibility to agents who consciously perceived morally relevant visual information compared to those who unconsciously perceived it. One challenge with this view is that people’s ability to perceive relevant information consciously and accurately is influenced by the neurocognitive state of the brain prior to the appearance of relevant visual information. In such cases, people do not have control over whether their prestimulus neurocognitive brain state will facilitate, impair, or distort accurate conscious perception. To explore some of these issues, we will present recent empirical work that evaluates (a) the cascading effect of prestimulus and stimulus-elicited neural activity on conscious and/or accurate visual perception and (b) how lay first-person responsibility judgments varied according to this conscious and/or accurate visual perception. We will also discuss how this work can inform competing philosophical theories about consciousness, control, and moral responsibility. Last, we will outline planned research that could extend our conclusions to different kinds of reason-responsive actions.