Thank Me With TEA!

Sensory World Disorders

Resources

Important

  • Debate on Cross-Modal Associations and Synesthesia – The question of whether cross-modal associations are a weaker version of synesthesia or fundamentally different phenomena is a major debate in cognitive science [11, 11:14]. Resolution requires collecting both behavioral and neurophysiological evidence [14, 11:43].
  • Main Elicitors for ASMR – Key triggers include watching individuals interact with objects, watching intimate social acts, hearing repetitive sounds, viewing simulated social interactions, and hearing whispering. The social context is often a critical factor.
  • ASMR Origin Evidence – The paper suggests ASMR arises from a reduced ability to inhibit emotional and sensory experiences, supported by neurophysiological evidence such as reduced functional connectivity in the default mode network and prefrontal regions, and reduced thalamic functional connectivity.
  • ASMR Paper Worksheet Questions – You should ensure you answer the assigned questions, as they will be discussed in the next session.

Core Concepts

  • Cross-Modal Associations: These are systematic regularities between senses that are population-level phenomena. Origins include magnitude matching (e.g., louder sound associated with bigger objects) and the brain picking up statistical regularities in the environment (e.g., higher pitch associated with higher areas in space or smaller objects).
  • Synesthesia: Defined as an uncommon, intense multisensory experience. Synesthetic associations often appear to be idiosyncratic, differing significantly between individuals, unlike cross-modal associations which are population-level and sometimes universal.
  • Behavioral Evidence in the Synesthesia Debate: Behavioral studies show mixed results, with some similarities (e.g., shared associations like A being red, B being blue, C being yellow; similar effects on reaction time) and differences (e.g., explainability, mapping, frequency, and transitivity) between synesthesia and cross-modal associations.
  • Congenital/Early Blindness (C/E) and Schizophrenia: Observations dating back to the 1950s suggest that C/E cortical blindness is protective against developing schizophrenia or other psychotic illnesses. This protective effect is specific to visual deprivation, as other C/E sensory losses (like deafness) do not reduce the risk.
  • Schizophrenia as a Cognitive Disorder: Many researchers view schizophrenia primarily as an information processing disorder, characterized by disturbances in perception, attention, memory, and language, with psychotic symptoms being secondary or compensatory features. Cognitive decline often precedes the onset of psychotic symptoms.
  • Sensory Diversity: Researchers are increasingly focused on identifying and appreciating the diversity of sensory experiences among people, suggesting that many experiences previously considered unusual are less rare than once thought (e.g., the Perception Senses project).

Theories and Frameworks

  • Neonatal Synesthesia Hypothesis: Posits that cross-modal associations and synesthesia originate from hyperconnectivity between sensory cortices present in infancy.
  • Cross-Activation Theory of Synesthesia: An extension of the neonatal hypothesis that adds genetics of pruning and hyperbinding by association cortices as factors explaining synesthesia, positioning it and cross-modal associations on a continuum.
  • Cognitive Account (Silverstein): Proposes that C/E blindness strengthens perceptual and cognitive functions (like auditory processing and memory) that are typically impaired in schizophrenia, thereby conferring a protective effect.
  • Predictive Processing Framework: Suggests that mental disorders result from errors in precision optimization, specifically imbalances between top-down predictions (priors) and incoming sensory evidence. Overweighting sensory evidence (underweighting priors) is associated with disorders like schizophrenia.
  • Predictive Processing Account of Schizophrenia (Pollak and Corlett): Suggests that C/E blindness forces the incremental and serial building of priors using non-visual modalities, promoting unique stability of these priors, which counters the weak priors associated with schizophrenia.

Notable Individuals

  • Steven M. Silverstein: Proposed the Cognitive account explaining how C/E blindness protects against schizophrenia.
  • Vera Morgan et al. (2018): Conducted a whole-population study supporting the finding that C/E cortical blindness is protective against schizophrenia.
  • Thomas A. Pollak and Philip R. Corlett (2020): Proposed the Predictive processing account of blindness being protective against schizophrenia.
  • Anil Seth: British neuroscientist who, with colleagues, started the Perception Senses project in 2022 to document the diversity of sensory experiences.
  • Helen Keller (1908): Described the serial nature of haptic and auditory processing, emphasizing how her mind had to piece together small parts of a surface over time.