LEFT BRAIN / RIGHT BRAIN Flashcards
The primary motor cortex
- rearmost bit of the frontal lobe
- management and execution of voluntary movements by transmitting information through the spinal cord to move to different parts of the body.
somatopic diagram of the primary motor cortex
a diagram of the brain which shows which parts of the brain control what body part. those parts that control areas that require more fine-grained control (e.g. hands) tend to be bigger.
how can we study the primary motor cortex
Transcranial Magnetic Stimulation (TMS)
Transcranial Magnetic Stimulation
is a way of temporarily altering the electrical activity of a small area of the brain’s cortex. When we know which area we have so affected, and also how that changed behaviour, we can test causal hypotheses about the function of the area in question.
spontaneous smiling
There are two neural control pathways in humans for generating facial expressions such as smiles. One pathway is for spontaneous expressions.
- Commands for spontaneous smiles originate in the basal ganglia, and are bilateral
– commands originating in either hemisphere affect both sides of the face.
voluntary smiling
the motor commands had to be initiated in the motor cortex, most likely in the LH.
The LH sends direct motor commands to the facial muscles to the right side of the face. Simultaneously, the LH also echoes the command to the RH over the corpus callosum. The RH in turn sends direct motor commands to the muscles of the left side of the face.
right hemisphere damage and smiling
a patient with damage to the RH affecting motor areas involved in generating voluntary expressions. When the patient smiles spontaneously, the action is natural and symmetrical, indicating that the basal ganglia pathway is intact. When he is asked to produce a smile, his LH is able to directly command the right side of his face, which produces the smile.
The RH is unable to pass on the LH’s command to the left side of the face (due to brain damage).
parkinsons disease and smiling
When a person has Parkinson’s disease, which involves loss of dopamine-producing cells in the substantia nigra (part of the basal ganglia) they can have a masked-face appearance in social interactions because they lose the ability to spontaneously react with facial expressions.
However, if asked to smile voluntarily, they can produce a symmetrical smile.
Parkinson’s and Substantia nigra
The substantia nigra atrophies (withers away through cell loss) in Parkinson’s disease. As these cells produce dopamine, a key neurotransmitter, their loss produces major effects on the central nervous system.
when trying to analyse a new complex image
the brain may carry out a broad-strokes, global analysis of the overall shapes and contours at the level of the whole scene to establish what sort of place it is, what the objects are, and what the scale of the scene is. The brain may then supplement this with a more fine-grained analysis of the more local areas of contrast and detail to see if adding this information helps clarify or disambiguate the course-grained analysis.
when trying to analyse familiar images
The visual brain must perform a multi-resolution analysis of the scene it faces to make sense of what’s there and what actions are possible in it. Faced with familiar, recognisable scenes, we don’t sense either the complexity or the effort involved in this
Hierarchical representation
This is a classic experimental paradigm (created by David Navon) for studying hierarchical representation of visual objects. Evidence suggests that the process of extracting the global shape takes precedence (although the details of this depends on various factors), and identifying the local structure is subject to delay as well as interference (where global and local structure clash).
LH appears to pick off local information and RH picks off global information in a rather extreme lateralisation effect
casual reasoning
trying to figure out (e.g.) a pattern, and what our brain does to do that
casual reasoning strategies
matching strategy
maximising strategy
matching strategy
The participants try to work out how often they get each shape, and guess that shape just that often. This is reasonable, but has the potential for high error rates because the series is random.
