Neurolinguistics

• Structures of the basal ganglia


  • Caudate
  • Putamen
  • Globes palladus (palladium)
  • Subthalamic nucleus
• Structures of the left inferior frontal gyrus (LIFG)


  • Pars orbital
  • Pars triangularis
  • Pars opercularis
• Broca's area


  Part of the left inferior frontal gyrus (LIFG)
• Arcuate fascicules


  Connects Broca's and Wernicke's areas
• Axon hillock


  Connects the soma to the axon and controls the initiation of the action potential
• Resting potential of neurons

  • -70 mV
• Threshold


  • -55 or -50 mV
• Broca's area (left frontal lobe) is involved in motor aspects of speech production.
• The hippocampus deals with long term memory, it's a sausage-shaped structure inside the temporal lobe.
• Wernicke's area (left posterior superior temporal gyrus) is involved in language comprehension.
• The amygdala is located deep within the brain and plays an important role in emotional processing.
• The cerebellum is responsible for coordinating movement and maintaining balance.
• The basal ganglia are responsible for planning and executing movement sequences.
• The thalamus acts as a relay station between different parts of the brain and helps to process sensory information.
• hippocampus (memory), broca's area, cerebellum (muscle control) and basal ganglia (speech planning, timing, turn taking, regulated behavior, etc) are all involved in language processing
• • commissural pathways: connecting two hemispheres
  • along the horizontal axis
  • for example the corpus callosum connects 2 hemispheres
• • projection pathways: cortical + subcortical connection
  • dorsoventral (descending)/ventrodorsal (Ascending)
• • association pathways
  • ipsilateral cortical areas (within same hemisphere)
  • longitudinal anterior/posterior
• depolarization is when sodium ions enter the neuron
• repolarization is when potassium ions leave the neuron
• BOLD signal peak at 5-10 seconds
• EEG measures electrical activity from scalp electrodes
• ERP measures event related potentials
• fMRI has low temporal resolution, but high spatial resolution
• • BOLD signal: five seconds after activation there will be the most oxygenated blood in a region
  • after the peak (5-6 sec after stimulus) there's dispersion and then an undershoot (lower oxygenated blood than original state)
  • returns to equilibrium from 16-32 seconds after (initial state)
• threshold = property of a neuron whereas weight is the property of the connection between neurons 
• AND gate activates output neuron only when both input neurons are active
• OR gate is inclusive usually-- output neuron can be activated when either one or both of the input neurons are active
• • excitation = total amount of input that the neuron receives
  • a is the activation value and w is the weight
  • each are sub k = of the same neuron
• k=1 is 'starts at 1' or start at the first neuron (you're not excluding any neurons)
• Hebbian learning = neurons that fire together, wire together. the learning rate is 0.1 (but this can vary)
• in Hebbian learning, if there is no change to the weights then it means that the inputs have already been learned
• the more often two neurons fire simultaneously, the stronger their synaptic connections become.
• • w is weight again, Wij (sub ij) is the weight of neurons i and j
  • t is time (current, right now time) delta t the future time (change in time)
  • Wij (t + delta t) is what the weight will be one step in the future
  • Wij (t) is the weight right now, + 0.1 (learning rate) times a sub i(activation value of i) times bj (activation value of neuron j)
  • the 0.1 divides the product of ai and bj by 10 which is the learning rate (can vary based on model)
• • ERP= event related potential, averaged EEG over time and participants
  • measured brain potential as a result of a stimulus— averaged across many observations (presentations of stimuli and participants)
  • ERPs are functionally specific
  • characteristics:
  • latency: when after a stimulus can we expect the ERP
  • polarity: positive/negative
  • location (in EEG: topography)
  • amplitude
• MEG= magnetoencephalography, measures magnetic fields generated by electrical currents in the brain
• an active brain region needs oxygenated blood in order to break down ATP for energy so that neurons can fire
• TR: time resolution, with which frequency (how long it took) to take one scan 
• TMS= transcranial magnetic stimulation, generates strong electromagnetism pulses to temporarily deactivate part of the cortex
• TE: echo time, how long it takes for the signal to return from the tissue back to the scanner