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Welcome to the nexus of ethics, psychology, morality, technology, health care, and philosophy
Showing posts with label Volition. Show all posts
Showing posts with label Volition. Show all posts

Thursday, November 1, 2018

Lesion network localization of free will

R. Ryan Darby, Juho Joutsa, Matthew J. Burke, and Michael D. Fox
PNAS
First published October 1, 2018

Abstract

Our perception of free will is composed of a desire to act (volition) and a sense of responsibility for our actions (agency). Brain damage can disrupt these processes, but which regions are most important for free will perception remains unclear. Here, we study focal brain lesions that disrupt volition, causing akinetic mutism (n = 28), or disrupt agency, causing alien limb syndrome (n = 50), to better localize these processes in the human brain. Lesion locations causing either syndrome were highly heterogeneous, occurring in a variety of different brain locations. We next used a recently validated technique termed lesion network mapping to determine whether these heterogeneous lesion locations localized to specific brain networks. Lesion locations causing akinetic mutism all fell within one network, defined by connectivity to the anterior cingulate cortex. Lesion locations causing alien limb fell within a separate network, defined by connectivity to the precuneus. Both findings were specific for these syndromes compared with brain lesions causing similar physical impairments but without disordered free will. Finally, our lesion-based localization matched network localization for brain stimulation locations that disrupt free will and neuroimaging abnormalities in patients with psychiatric disorders of free will without overt brain lesions. Collectively, our results demonstrate that lesions in different locations causing disordered volition and agency localize to unique brain networks, lending insight into the neuroanatomical substrate of free will perception.

The article is here.

How much control do you really have over your actions?

Michael Price
Sciencemag.org
Originally posted October 1, 2018

Here is an excerpt:

Philosophers have wrestled with questions of free will—that is, whether we are active drivers or passive observers of our decisions—for millennia. Neuroscientists tap-dance around it, asking instead why most of us feel like we have free will. They do this by looking at rare cases in which people seem to have lost it.

Patients with both alien limb syndrome and akinetic mutism have lesions in their brains, but there doesn’t seem to be a consistent pattern. So Darby and his colleagues turned to a relatively new technique known as lesion network mapping.

They combed the literature for brain imaging studies of both types of patients and mapped out all of their reported brain lesions. Then they plotted those lesions onto maps of brain regions that reliably activate together at the same time, better known as brain networks. Although the individual lesions in patients with the rare movement disorders appeared to occur without rhyme or reason, the team found, those seemingly arbitrary locations fell within distinct brain networks.

The researchers compared their results with those from people who lost some voluntary movement after receiving temporary brain stimulation, which uses low-voltage electrodes or targeted magnetic fields to temporarily “knock offline” brain regions.

The networks that caused loss of voluntary movement or agency in those studies matched Darby and colleagues’ new lesion networks. This suggests these networks are involved in voluntary movement and the perception that we’re in control of, and responsible for, our actions, the researchers report today in the Proceedings of the National Academy of Sciences.

The info is here.

Friday, August 11, 2017

The real problem (of consciousness)

Anil K Seth
Aeon.com
Originally posted November 2, 2016

Here is an excerpt:

The classical view of perception is that the brain processes sensory information in a bottom-up or ‘outside-in’ direction: sensory signals enter through receptors (for example, the retina) and then progress deeper into the brain, with each stage recruiting increasingly sophisticated and abstract processing. In this view, the perceptual ‘heavy-lifting’ is done by these bottom-up connections. The Helmholtzian view inverts this framework, proposing that signals flowing into the brain from the outside world convey only prediction errors – the differences between what the brain expects and what it receives. Perceptual content is carried by perceptual predictions flowing in the opposite (top-down) direction, from deep inside the brain out towards the sensory surfaces. Perception involves the minimisation of prediction error simultaneously across many levels of processing within the brain’s sensory systems, by continuously updating the brain’s predictions. In this view, which is often called ‘predictive coding’ or ‘predictive processing’, perception is a controlled hallucination, in which the brain’s hypotheses are continually reined in by sensory signals arriving from the world and the body. ‘A fantasy that coincides with reality,’ as the psychologist Chris Frith eloquently put it in Making Up the Mind (2007).

Armed with this theory of perception, we can return to consciousness. Now, instead of asking which brain regions correlate with conscious (versus unconscious) perception, we can ask: which aspects of predictive perception go along with consciousness? A number of experiments are now indicating that consciousness depends more on perceptual predictions, than on prediction errors. In 2001, Alvaro Pascual-Leone and Vincent Walsh at Harvard Medical School asked people to report the perceived direction of movement of clouds of drifting dots (so-called ‘random dot kinematograms’). They used TMS to specifically interrupt top-down signalling across the visual cortex, and they found that this abolished conscious perception of the motion, even though bottom-up signals were left intact.

The article is here.