Navigation, Taste, Smell, Multisensory Integration Flashcards
What are the 4 different cell types of spacial orientation?
Head direction cells: Dorsal thalamus, subiculum
Location - Place cells: Hippocampus
Location map – grid cells: Entorhinal cortex
Location boundaries – border cells: Entorhinal cortex
Describe head direction cells
HD cells fire as a function of head direction in the horizontal plane (Direction of head, not body position.)
Fires whether animal is moving or still.
Firing is independent of location and behavior.
Each cell exhibits one preferred firing direction.
Preferred firing directions distributed equally around 360º.
Little adaptation in cell firing when the rat holds its head in the cell’s preferred firing direction.
How does an HD cell respond when a rat locomotes
inverted, upside-down on the ceiling ?
Loss of directional tuning on ceiling, with increased background firing rate.
Describe grid cells
Grid cells have ordered fields with hexagonal structure
Grid fields form instantly in a new environment
Neighboring MEC grid cells have similar fields.
Nearby cells fields are similar in spacing, but displaced by differences in spatial phase
Grid fields size is topographic
Dorsal Medial Entorhinal Cortex (MEC) cell fields are small dorsally, larger ventrally
MEC grid cells modulate on top of theta rhythm
Describe place cells in the hippocampus
A – recording location in CA1 of hippocampus
B – Place fields of pyramidal cells differ in the spatial environment, with primarily one location prominent for each cell.
CA place cells do not provide heading information (heading info is provided by head direction cells)
Place cells respond regardless of direction, only signal allocentric location
Ex: Bat flies in open arena. Place cells form 3D cloud fields of excitation. Different cells form different place fields that create cognitive spatial map.
What are the 5 primary tastes?
Sweet (sugars) Salty (salts) Sour (acids) Bitter (quinine) Umami (MSG)
Where are taste buds located?
Taste buds located on tongue (papillae) and epithelial surface of palate, pharynx, & larynx
What are the 4 types of papillae (on tongue)?
Four types of papillae Filiform (no taste buds) Fungiform Foliate Circumvallate
Describe taste bud receptors
Tastants enter pore
Receptor channels in microvilli project into pore
Receptors sensitive to different tastants
Cells turn over every 7 – 10 day
Describe taste transduction
Receptor channel transduction:
Salts, sour acids (HCl) enter ion gated channel (ionotropic)
Sweet, bitter, amino acid mostly
2nd messenger G-protein receptors
Describe the central taste pathway
Taste afferents terminate in the nucleus of the solitary tract:
VII – anterior 2/3 of tongue (chorda tympani) and palate
IX – vallate and foliate papillae
X - posterior oral cavity
NTS projects to ventral posterior medial nucleus of thalamus
VPM projects to area 3b (anterior insular cortex)
Pathway responsible for discrimination of taste
How do NTS neurons respond to different tastants?
Excitatory response to salts, acids, and bitter stimuli
Inhibitory response to sugars
- Classified as a salt best cell
Describe multidimensional scaling of taste space
Multidimensional scaling analysis of responses from 30 taste cells to different tastants :
Quality is discriminated by the distance between similar spaced groups of compounds.
Notice that taste neurons discriminate the four major qualities of tastants based upon relative response similarities
Results in a “taste space” map of three major factors
What is the pathway for the taste cortex?
VPM projects to area 3b (anterior insular cortex in post-central gyrus)
Bifurcation projection to the frontal operculum taste cortex
Describe the topographic organization of the taste cortex?
Sweet, sour, salty, bitter, and umami qualitites have different representations in oral cavity receptors
Quality is represented in different regions of neighboring cortex
Receptor topography gives rise to cortical quality
Results in a “taste space” map in cortex
