L8- Driving & Navigation Flashcards
What 2 key areas in macaques have been highlighted for navigation?
-Dorsal Medial Superior Temporal Cortex (MSTd), which responds to optic flow
-Ventral Intraparietal Area (VIP), which appears to be sensitive to heading
What does driving involve?
-Actively controlling direction of motion
-Changing heading at an appropriate rate to steer smoothly
-Monitoring errors and correcting them
-Navigation through the spatial world
What do structural MRI scans of the brain show?
-Bone & fat appear white
-Fluid appears dark
-Cortical white matter has higher fat content (myelinated neurons) than grey matter, so appears lighter
What do functional MRI scans show?
-Blood oxygen level dependent (BOLD) signal provides measure of brain activity
-Haemoglobin carries oxygen, and transfers it to tissue needing energy
-Deoxygenated blood 20% greater magnetic susceptibility
-Localised magnetism disrupts homogeneity of scanner’s magnetic field
-Thus, blood flow to region provides indirect measure of activity
How are fMRI’s carried out to determine active brain regions?
-Brain volumes under many conditions are recorded, and volumes subtracted to remove the activity in common between events
-Reveals areas associated with each event
Outline the method of Spiers & Maguire’s (2006;2007) london taxi study
-Virtual taxi, real taxi drivers
-Driving point to point, navigating the best route
-Navigation component (destination, route, & changes to route)
-Driving component (obeying rules, avoiding vehicles, negotiating junctions)
-Encoded events retrospectively (visual and verbal descriptions)
-Examined prepared, & unprepared actions, and planning/monitoring/rules
What were the findings of Spiers & Maguire (2006;2007)?
-Different parietal regions involved in unprepared actions
2 pathways related to turning at junction:
-Dorsal - Occipital to Superior Parietal
-Ventral- Occipital to Posterior Middle Temporal Gyrus
Outline Walter et al. (2001)
-Active or passive driving (virtual) around hamburg
-Active driving more ventral stream than baseline; more parietal than passive
-Passive driving more both than baseline & active
Outline experiment 1 results from Field, Wilkie & Wann (2007) on self motion & future path activations.
Self-motion:
-Compared flow (optic?) with baseline
-Self-motion activated VIP
Future path:
-Compared road and no road condition
-Activated mainly bilateral superior parietal lobule (SPL), close to PEF (parietal eye fields)
-Also activates Middle-Temporal complex
-horizontal road condition- left activation around MT complex
Outline experiment 1 results from Field, Wilkie & Wann (2007) on steering errors & steering corrections
Steering errors:
-heading and steering conditions (with/without error)
-visual steering errors activate mainly left SPL, just anterior to future path area
Steering corrections:
- cerebellum, medial frontal cortex, dorsal premotor cortex
Outline experiment 2 results from Field, Wilkie & Wann (2007)
-Repeated method with fixation, serial saccade task, & measured gaze shifts
-Saccade localizer task activated PEF, like in future path
-Other parts of PEF in future path not activated by saccade localizer task, thus involved in future path processing
