Related Experiment Video
Updated: Jan 7, 2026
07:30
Brain Morphology of Cannabis Users With or Without Psychosis: A Pilot MRI Study
Published on: August 18, 2020
7.4K
Posterior parietal cortex modulates perceptual decisions depending on psychotic phenotype
Francesco Scaramozzino1, Ryan McKay1, Nicholas Furl1
1Royal Holloway, University of London, UK.
Neuropsychologia
|December 26, 2025
Summary
Repetitive transcranial magnetic stimulation (TMS) over the posterior parietal cortex (PPC) altered decision-making in healthy individuals but not those with psychotic phenotypes, suggesting altered PPC excitability in psychosis.
Area of Science:
- Neuroscience
- Cognitive Psychology
Background:
- Psychotic phenotypes are linked to reduced data gathering and altered sensory precision, particularly in tasks involving the posterior parietal cortex (PPC).
- Posterior parietal cortex (PPC) excitability, modulated by 1 Hz repetitive transcranial magnetic stimulation (TMS), was investigated for its differential effects on these behavioral patterns in high versus low psychotic phenotypes.
Purpose of the Study:
- To investigate whether modulating posterior parietal cortex (PPC) excitability using repetitive transcranial magnetic stimulation (TMS) differentially affects sensory precision and data-gathering decisions in individuals with high versus low psychotic phenotypes.
- To test the hypothesis that delusional and hallucinatory traits moderate TMS effects on sensory precision (drift rates) and decision thresholds.
Main Methods:
- A total of 68 participants were divided into two groups, undergoing either TMS or sham-TMS over the right PPC.
- Performance was compared using the random dot motion (RDM) and beads tasks.
- Hierarchical drift-diffusion models were employed to estimate drift rates (sensory precision) and decision thresholds, examining interactions with delusional and hallucinatory phenotypes.
Main Results:
- In the random dot motion (RDM) task, TMS increased decision thresholds in the low psychotic phenotype group, an effect absent in higher psychotic phenotype groups.
- Drift rates were reduced in participants with higher delusional phenotypes.
- No significant effects were observed on the beads task.
Conclusions:
- The findings indicate a causal role for the posterior parietal cortex (PPC) in decisions to terminate data gathering during perceptual inference.
- The absence of TMS effects on decision thresholds in the psychotic phenotype group suggests novel hypotheses regarding PPC excitability's role in the neural mechanisms underlying decision-making in psychosis.
Related Concept Videos
01:23Somatosensory, Motor, and Association Cortex
2.1K
The somatosensory cortex in the parietal lobes is crucial for interpreting sensory data such as touch, temperature, and proprioception. The somatosensory cortex, situated in the parietal lobes, plays a vital role in interpreting sensory information like touch, temperature, and proprioception—awareness of body position. This specialized brain region features an organized structure wherein neurons at the top primarily process sensations originating from the lower body. In contrast, those at...
2.1K
01:14Motor and Sensory Areas of the Cortex
6.8K
The cerebral cortex, the brain's outermost layer, is pivotal in processing complex cognitive tasks, emotions, and various sensory inputs and executing voluntary motor activities. This intricate structure is divided into three primary functional areas: the motor areas, sensory areas, and association areas.
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex....
Motor Areas
The motor areas located in the frontal lobe are central to controlling voluntary movements. This region is further subdivided into the primary motor cortex and the premotor cortex....
6.8K
01:33Somatosensation
42.9K
The somatosensory system relays sensory information from the skin, mucous membranes, limbs, and joints. Somatosensation is more familiarly known as the sense of touch. A typical somatosensory pathway includes three types of long neurons: primary, secondary, and tertiary. Primary neurons have cell bodies located near the spinal cord in groups of neurons called dorsal root ganglia. The sensory neurons of ganglia innervate designated areas of skin called dermatomes.
42.9K
01:21Association Areas of the Cortex
8.7K
Association areas are regions of the cerebral cortex that do not have a specific sensory or motor function. Instead, they integrate and interpret information from various sources to enable higher cognitive processes such as memory, learning, and decision-making. Some key association areas include the following:
Prefrontal Association Area: This area is located in the frontal lobe and is involved in planning, decision-making, and moderating social behavior. It connects with primary motor areas,...
Prefrontal Association Area: This area is located in the frontal lobe and is involved in planning, decision-making, and moderating social behavior. It connects with primary motor areas,...
8.7K
01:25Factors Affecting Perception
2.6K
Perception is influenced by perceptual set, context, motivation, and emotion. Perceptual set, or perceptual expectancy, refers to the tendency to perceive things in a particular way, influenced by previous experiences and expectations. This phenomenon affects the interpretation of stimuli, creating a set of mental tendencies and assumptions that impact sensory perceptions of sound, taste, touch, and sight.
An illustrative example of a perceptual set is the scenario where an airline pilot told...
An illustrative example of a perceptual set is the scenario where an airline pilot told...
2.6K
01:20Parallel Processing
597
The brain processes sensory information rapidly due to parallel processing, which involves sending data across multiple neural pathways at the same time. This method allows the brain to manage various sensory qualities, such as shapes, colors, movements, and locations, all concurrently. For instance, when observing a forest landscape, the brain simultaneously processes the movement of leaves, the shapes of trees, the depth between them, and the various shades of green. This enables a quick and...
597