Week 6B Chemical Senses and Multisensory Integration

Flashcards covering the chemical senses of taste and smell, individual differences in perception, and the principles of multisensory integration and illusions based on the PSYC11212 lecture.

Chemosenses

The category of senses, including taste (gustation) and smell (olfaction), that function by detecting chemicals.

Gustation

The technical term for the sense of taste, used for identifying chemicals and preventing the ingestion of toxins.

Olfaction

The technical term for the sense of smell, which can discriminate up to $10,000$ types of molecules.

Core tastes

The five primary taste categories: Sweet, Sour, Salty, Bitter, and Umami.

Taste bud cell

A biological unit containing taste receptors that respond to each of the core tastes.

Umami

A core taste caused by substances such as Mono sodium glutamate, Inosine $5'$-monophosphate, or Guanosine $5'$-monophosphate.

Supertasters

Individuals who possess more papillae and taste buds, allowing them to detect the substance $PROP$.

PROP (6-n-propylthiouracil)

A substance often described as 'tasteless' that can be detected by individual supertasters.

Starch flavour

A potential sixth taste suggested by a $2016$ study that may be important for detecting a slow-release form of energy.

Orthonasal

The route to olfactory perception that occurs via inhalation through the nose.

Retronasal

The route to olfactory perception that occurs during the actions of chewing and swallowing.

Olfactory receptors

The system comprising $350$ different types of receptors where those of a similar type project to the same glomerulus.

Glomerulus

The specific structure in the olfactory system where receptors of a similar type project their signals.

Top-down effects on smell

Cognitive influences such as attention, sniffing, and labeling (e.g., body odour versus cheese) that alter olfactory perception.

Proust effect

The phenomenon where particular smells bring back vivid memories, attributed to the linkage between smell and the limbic system.

Limbic system

The brain system associated with emotion that has a close connection to the sense of smell.

Flavour

A multisensory experience defined as the combination of Taste and Olfaction.

Somatosensory cortex

The area of the brain where the tongue is well represented, facilitating the perception of food texture.

Chilli suppression

The reduction of pain receptor activity in the tongue, most effectively achieved by sweet and sour liquids.

Multisensory stimulus

A stimulus that generates several independent energies which are simultaneously detectable by different types of sensory receptors.

Orbitofrontal cortex

An area containing multisensory receptive fields where a single neurone may respond to both the taste and sight of a banana.

Posterior parietal cortex

An area where cells respond to multiple modalities, such as touch to the index finger and visual stimuli close to that finger.

Multisensory integration

The process of joining information from different senses to detect weak stimuli, resolve ambiguity, or alter stimulus quality.

Multisensory Receptive Fields

Single neurons can respond to more than one modality.

Orbitofrontal Cortex

Integrates taste and smell (e.g., the taste of a banana combined with the sight of a banana).

Posterior Parietal Cortex

Integrates touch, vision, and audition. For example, a cell responding to a touch on the index finger might also fire when seeing a visual stimulus near that finger.

Purpose of Integration:

1. Allows for the detection of weak stimuli in another modality.

2. Resolves ambiguity in a stimulus from a single modality.

3. Can alter the perceived quality of a stimulus in another modality.

Ventriloquism

An effect where visual information influences where in space an individual perceives a sound source to be.

Visual capture

The phenomenon that allows us to follow the action in a cinema or on a TV by linking sound to visual cues.

McGurk effect

A multisensory illusion where watching specific lip movements (e.g., 'ga-ga') while hearing a different sound (e.g., 'ba-ba') results in a third perceived sound (e.g., 'da-da').

Rubber Hand Illusion

An illusion in which an individual perceives a rubber hand as their own due to synchronized visual and tactile input.

Kinaesthesia illusion

An illusion of speed occurring when the nervous system turns down the 'gain' on steady-state inputs, such as driving at a constant $70 \text{ mph}$.

Synaesthesia

A condition affecting approximately $1 \text{ in } 200$ people where stimulation of one sense leads to an automatic experience in another sense.

Crossmodal correspondences

Non-arbitrary associations between different sensory modalities, exemplified by the Bouba and Kiki effect.

Subjective Experience of Synaesthesia

• Subjective Experience: Luria ($1968$) documented a case: "It looks something like fireworks tinged with a pink-red hue. The strip of color feels rough and unpleasant and it has an ugly taste – rather like that of a briny pickle."

• Verification: Synaesthesia is considered "real" and can be demonstrated through visual search tasks (e.g., spotting a triangle of '2's among '5's where colors assist the search).

Bouba/Kiki Effect

A non-arbitrary mapping between speech sounds and the visual shape of objects. People consistently identify jagged shapes as "Kiki" and rounded shapes as "Bouba."

Contributing Factors to Food Perception:

• Texture: The tongue is heavily represented in the somatosensory cortex. Texture is a major factor in food preference; for example, mushrooms are often disliked solely due to their texture.

• Pain: Chilli contains capsaicin which acts on pain receptors in the tongue. This sensation can be suppressed by other tastes:

  • Best suppressors: Sweet and sour liquids.

  • Intermediate: Salty liquids.

  • Ineffective: Bitter liquids.

• Sound:

  • Foods are rated as crunchier and fresher when the sound of the crunch is amplified or high frequencies are increased.

  • Background noise can reduce the perceived intensity of sweetness and saltiness.

• Vision:

  • In one study, oenology (wine) students were fooled into describing a white wine with red dye as having the characteristics of a red wine.

  • Tastiness ratings for dishes increase when the presentation is art-inspired ("We eat first with our eyes").