PY2507.7 ~ {Navigational impairments}
Siegel and White (1975):a hierachical model: 3 diff levels [stages] for navigational profiency
spatialknowledge: landmark processing + route processing + survey processing
landmark processing
individuals have ability to perceptually discriminate and recognize landmarks
egocentric navigation
route processing
individuals can use directional info based on ego centric representation as well as landmarks [turn left at this landmark to reach the next one]
egocentric navigation
survey processing
individuas can rely on global representation of enviro, like a map
allocentric navigation
spatial knowledge
a person's understnding of the layout, structure and relationships between places or objects in an enviro [landmark,route & survey]
what did Montello (1988) argue about stages of spatial knowledge
that there are no pure separate stages, survey knowledge begins forming right from the first exposure
how does spatial knowledge change with experience, according to Montello
changes quantitatively - you gather more info, but the type of knowledge stays similar
do all individuals acquire spatial knowledge the same way
no - individuals diff mean that even with the same exposure, peope vary in their spatial understanding
is spatial knowledge only metric [map-like] or linguistic
can be both - linguistic spatial knowledge [verbal directions] exists alongside metric spatial knowledge and is not just a precursor to it
what are the 3 diff dorsal pathways involved in sk
parieto-premotor pathway supports visually-guided actions
parieto-prefrontal pathway supports s processing and memory
parieto-medial temporal pathway that supports navigation
retrosplenial cortex
found in posterior cingulate cortex [behind corpus callosum]
helps translate between egocentric (self-centered) & allocentric (map-like) representations, crucial for using landmarks to navigate & for integrating spatial memory with current perception.
parahippocampul cortex
located in medial TL adjacent to hippocampus
involved in scene recognition & contextual spatial memory, helps encode + retrieve the layout of places & is part of the parahippocampal place area (PPA).
what happens is sretrosplenial cortex is damaged
can cause topographicl disorientation - people may recognize landmarks but be unable to use them to navigate
what theory did O'Keefe and Nadel (1978) propose about the hippocampus
the Cognitive Map Theory - states that hippocampus constructs internal maps of spatial enviros for navigation
what are place cells and where are they found
neurons in the hippocampus that fire when an individual is in a specific location - support the brain's ability to form spatial maps
what evidence supports the role of the hippocampus in navigation
discovery of place cells (O'Keefe & Dostrovsky, 1971) + impaire navigation in patients with hippocampal damage (Smith & Milner, 1989) + neuroimaging studies showing hippocampal activation during spatial tasks (Maguire et al., 1998; Hartley et al., 2003)
what did Maguire's study of London taxi drivers reveal
experienced taxi drivers has larger posterior hippocampi, suggesting structural changes due to long-term spatial navigation
place cells in humans Ekstrom et al. (2003)
[like animals] most densely clustered in the hippocampus - they recorded brain activity in patients with implanted electrodes as they explored virtual towns
which brain regions responded to diff spatial feaures in Ekstrom et al's study
hippocampus - specific locations [place cells] + parahippocampal region - landmarks + frontal lobes - goal-related behaviour + amygdala - some spatial activity, less specific
head cells
fire when animals are heading in a certain direction, first described by James Ranck (1985) in hippocampal formation [subiculum]
grid cells
fire in a regular triangular array or grid of locations, possibly elements of a metric system for spatial navigation - first discovered in the entorhinal cortex (Hafting et al., nature 2005)
who won the joint nobel prize in Physiology or Medicine 2014
John O'Keefe and May-Britt Moser and Edvard I. Moser for their discoveries of cells that constitute a positioning system in the brain
the parahippocampal place area [PPA]
a region in posterior parahippocampal corex that responds preferentially to pics of places / landmarks (Epstein & Kanwisher, 1998)
what do parahippocampal lesions [both anterior and posterior] result in
pposterior - landmark agnosia [damage to lingual gyrus as well]
anterior - anterograde disorientation [sometimes retrospinal cortex]
landmark agnosia
patients report they cannot identify topographical entities such as buildings or streets [sometimes they compensate for this impairment by focusing on particular obj in enviro
prosopagnosia, achromatopsia and visual field deficit can co-occur
anterograde disorientation
exhibit prob of spatial memory - difficulty learning and navigating new enviro despite being able to navigate familiar places normally [known at east 6 months before lesions]
retrospinal cortex lesions - heading disorientation
can visually recognize places and buildings, but can't use these landmarks for purposes of orientation [they can look at building & name it but not any other location nearby which is not immediately visible + ego-allocentric transformation probs
What is egocentric navigation and which brain areas support it?
relies on landmarks and turn-based routes from your perspective, involves PPA, parietal cortex [precuneus, cuneus, inferior parietal lobule] retrosplenial cortex
What is allocentric navigation and which brain areas support it?
uses map-like (survey) strategies, relies on hippocmpus [place cells], entorhinal cortex [grid cells]
What’s the key difference between egocentric and allocentric navigation?
e - self centered perspective using routes & landmarks
a - bird's-eye/map-like view using spatial relationships between locations
egocentric disorientation
follows right or bilateral posterior PL lesions - inability to: represent the location of enviro obj with respect to self + point towards locations when eyes closed + learn or recall appropriate spatial direction + disorientation in both novel and familiar environment [landmark recognition is fine, often associated with other visuo-spatial deficits]
corsi test
test of visuo-spatial memory [not directly related to navigational skills cause processing micro visuo-spatial space can be spared in patients with damage to macro [navigational] space
assessment of navigational disorders
virtual reality vs real enviro tasks + landmark recog + route learning + WaICT + map following + route/map drawing
rarely evaluated in current clinical neuropsych practice + suitable diagnostic instruments are lacking -
WaICT [walking corsi test]
route learning in experimental setting (Piccardi et al., 2014) - participants are asked to learn and reproduce sequences of spatial locations by walking a path shown by experimenter
map draawing
drawing a map of a familiar enviro or an enviro explored with examiner used to assess survey representation skills
morris water maze
studies spatial learning and memory [esp rodents], animal placed in diff locations in pools across trials + must use visual cues around room to learn platform's fixed location overtime animal swims more directly to platform
developmental topographical disorientation
a deficit in development of landmark, route or survey knowledge in context of normal intellectual ability in absence of any known perinatal, neurological or psychiatric disorders - selective developmental deficit