Thermosensory Perceptual Learning Is Associated with Structural Brain Changes in Parietal-Opercular (SII) Cortex

Area of Science:

• Neuroscience
• Sensory Perception
• Human Brain Imaging

Background:

• The precise location of the human sensory cortex responsible for temperature perception is debated.
• Both the parietal-opercular cortex (SII) and posterior insula are implicated in thermosensory processing.
• Neither region has been definitively identified as the primary site for fine temperature discrimination.

Purpose of the Study:

• To investigate perceptual learning in human temperature discrimination.
• To identify the neuroanatomical correlates of enhanced temperature discrimination.
• To resolve the debate regarding the location of the 'temperature cortex'.

Main Methods:

• A perceptual learning paradigm involving repetitive training over 5 days.
• Behavioral assessments of discrimination accuracy for warmth and cool detection.
• Structural magnetic resonance imaging (MRI) to detect changes in gray matter volume.

Main Results:

• Participants showed improved discrimination accuracy for both warm and cool stimuli after training.
• Increases in accuracy were specific to the trained temperature (warm or cold).
• Symmetrical increases in gray matter volume were observed in the parietal-opercular cortex (SII).
• Distinct, adjacent regions within SII were identified for cold and warm discrimination, with cold being more anterior.

Conclusions:

• Perceptual learning can enhance the human temperature discrimination system.
• Structural plasticity, evidenced by gray matter increases, occurs in the parietal-opercular cortex (SII), not the posterior insula.
• The findings provide strong evidence for SII as the 'temperature cortex' and suggest functionally distinct, temperature-specific processing modules within it.