Mental Imagery in Cognitive Neuroscience

Mental Imagery

• Mental imagery refers to the visual and sensory representations created in our minds without the presence of external stimulation.
• These images preserve the perceptual properties of stimuli they represent (Kosslyn et al., 2006).
• Mental imagery relies on top-down processing, which means our prior knowledge and experiences influence the content of our mental images.

Historical Perspectives on Mental Imagery

• Plato: Suggested that memories are like stamp images created from wax, indicative of the private and introspective nature of mental representations.

• Behaviorism: Figures like Watson (1913) denied the existence of mental images, viewing the mind as a "black box."

• This skepticism had a lingering negative effect on mental imagery research.

• 1970s Developments: Emphasis shifted, recognizing mental imagery as integral to memory, problem-solving, and creativity (e.g., Paivio, 1971).

• Shepard and Metzler (1971): Conducted studies using the mental rotation paradigm, showing that response times increased linearly with the angular disparity between two 3D objects, indicating cognitive manipulation involved in visual rotation.

The Imagery Debate: Analog vs. Propositional Representation

• Analog Code (Kosslyn):

  • Proposes that mental images act as depictive representations, corresponding analogously to real objects.
  • Key features include:
  • Each part of a mental representation corresponds to the actual parts of the object.
  • Distances in the mental representation relate to actual distances on the object.

• Image Scanning Paradigm (Kosslyn, Ball and Reiser, 1978): Study where participants imagined walking around an island on a mapped representation; found that scanning time increased linearly with distance, supporting the analog representation theory.

• Propositional Code (Pylyshyn):

  • Argues mental imagery uses a nonexistent visual-map system but instead relies on descriptive representations akin to language.
  • This type does not preserve the visual or spatial characteristics of the original stimuli.

Neuroimaging Studies and Visual Mental Imagery

• To resolve the imagery debate, researchers leverage neuroimaging techniques:

  • fMRI and PET studies indicate visual imagery may engage similar brain areas as visual perception (Kosslyn, 1994).
  • TMS or lesions provide evidence about the causative role of certain brain areas in mental imagery.

• Findings show that the visual cortex is active during imagery tasks, suggesting shared substrates between perception and imagery.

  • Positive correlation exists between activity in the visual cortex and the vividness of the imagery (Amedi et al., 2005).

Neural Mechanisms of Visual Mental Imagery

• Pearson (2019) noted:

  • Voluntary mental imagery relies on combinations of retrieved memory information, making it hard to visualize unprecedented content.
  • Frontal areas coordinate spatial and sensory information but don’t hold imagery content.
  • The hippocampus is likely involved in spatial and memory aspects of imagery.

• Main research focus on visual cortex (V1, V2) where early activity patterns emerge in both perception and imagery.

• Damage to the ventral (what) and dorsal (where) streams from ventral pathway (VP) damage impairs object perception and shape visualization.

Applications and Implications of Mental Imagery

• Mental imagery has applications in various domains, including:
  • Navigation
  • Creativity
  • Sports and motor control.
• It plays a role in memory (e.g., episodic memory and eyewitness memory) and impacts processes like decision making and reading comprehension.

Vividness of Visual Imagery Questionnaire (VVIQ)

• A tool to assess the vividness of visual imagery:
  • Rates on a scale from 1 (no image) to 5 (as vivid as real seeing).
  • Participants imagine various scenarios (faces of friends, natural scenes, shop appearance) and rate the vividness of their imagery.

Aphantasia

• Defined as the inability to voluntarily experience object imagery (Zeman et al., 2015).
• Case study of M.X. showcased non-linear response times in tasks but intact spatial imagery using alternative strategies.
• Aphantasia highlights the variability in human imagery ability, emphasizing the flexibility of cognitive strategies individuals may employ in tasks.