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Imaging tactile imagery: Changes in brain connectivity support perceptual grounding of mental images in primary sensory cortices

DOI: 10.1016/j.neuroimage.2014.05.014
Schmidt, T. T., Ostwald, D., & Blankenburg, F. (2014). Imaging tactile imagery: changes in brain connectivity support perceptual grounding of mental images in primary sensory cortices. NeuroImage, 98, 216–224. doi:10.1016/j.neuroimage.2014.05.014

Abstract

Constructing mental representations in the absence of sensory stimulation is a fundamental ability of the human mind and has been investigated in numerous brain imaging studies. However, it is still unclear how brain areas facilitating mental construction processes interact with brain regions related to specific sensory representations. In this fMRI study subjects formed mental representations of tactile stimuli either from memory (imagery) or from presentation of actual corresponding vibrotactile patterned stimuli. First our analysis addressed the question of whether tactile imagery recruits primary somatosensory cortex (SI), because the activation of early perceptual areas is classically interpreted as perceptual grounding of the mental image. We also tested whether a network, referred to as ‘core construction system’, is involved in the generation of mental representations in the somatosensory domain. In fact, we observed imagery-induced activation of SI. We further found support for the notion of a modality independent construction network with the retrosplenial cortices and the precuneus as core components, which were supplemented with the left inferior frontal gyrus (IFG). Finally, psychophysiological interaction (PPI) analyses revealed robust imagery-modulated changes in the connectivity of these construction related areas, which suggests that they orchestrate the assembly of an abstract mental representation. Interestingly, we found increased coupling between prefrontal cortex (left IFG) and SI during mental imagery, indicating the augmentation of an abstract mental representation by reactivating perceptually grounded sensory details.

Authors

  • Timo Torsten Schmidt1
  • Dirk Ostwald1
  • Felix Blankenburg1

Understanding How Our Brain Constructs Mental Images

Overview/Introduction

Have you ever imagined the feeling of a soft fabric or the texture of a rough surface without actually touching it? This ability to create mental images in the absence of physical stimuli is a fascinating feature of the human brain. A recent study explored how different parts of the brain work together to form these mental representations, particularly focusing on tactile (touch-related) imagery. The researchers aimed to understand how brain areas involved in mental construction interact with those responsible for processing sensory information.

Methodology

The study involved 14 healthy volunteers who participated in an experiment using functional magnetic resonance imaging (fMRI) to observe brain activity. Participants were asked to form mental images of tactile patterns either from memory or by actually feeling the patterns through a special device. The experiment consisted of three conditions:
  • Perception: Participants felt a vibrotactile pattern and identified if a probe was part of it.
  • Imagery: Participants imagined the pattern and performed the same task as in the perception condition.
  • Control: Participants detected a brief interruption in the probe's vibration without any pattern.
The researchers analyzed brain activity to see which areas were activated during these tasks and how they interacted with each other.

Key Findings

  • Activation of Sensory Areas: The study found that imagining tactile patterns activated the primary somatosensory cortex (SI), a brain area typically involved in processing actual touch sensations. This suggests that mental imagery is "grounded" in sensory experiences.
  • Core Construction System: A network of brain regions, including the retrosplenial cortices, precuneus, and left inferior frontal gyrus (IFG), was identified as crucial for constructing mental images. These areas were active during the imagery tasks, indicating their role in assembling mental representations.
  • Increased Connectivity: The study revealed enhanced connectivity between the prefrontal cortex (specifically the left IFG) and the SI during mental imagery. This suggests that the brain augments abstract mental images by reactivating sensory details.

Implications

These findings have significant implications for understanding how our brains create and manipulate mental images. The study highlights the brain's ability to use sensory information to enrich mental representations, which could be useful in fields like psychology, education, and even virtual reality development. Understanding these processes could also aid in developing therapies for individuals with sensory processing disorders.

Limitations

While the study provides valuable insights, it involved a small sample size of 14 participants, which may limit the generalizability of the findings. Future research with larger and more diverse groups is necessary ...