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March 11, 2021

[Brain Image]    

PSY 340 Brain and Behavior

Class 13: Brodmann Areas & Large-Scale Brain Networks (Outline)

   


Korbinian BrodmannThe Problem Solved by Korbinian Brodmann (1868-1918)

How can we identify subregions of the cortex in a way which would be understood by scientists in different nations who spoke different languages?

He creates a cytoarchitectonic map (that is, a map of the surface of the cortex in which similar kinds of cells (both layers and columns) are grouped together and numbered). These are called Brodmann Areas (BAs) and neuroscientists regularly use Brodmann numbers in their scientific reports to identity where on the cortex they are focusing.

Brodmann's original map

Brodmann Areas/Numbering of Lobes of Left
                  Hemisphere




Networks of the Brain
Research Methods

1. fMRI (Functional Magnetic Resonance Imaging): see notes from last class

Isotopic vs. anisotropic movement2. DTI
(Diffusion Tensor Imaging) aka Diffusion MRI
  • Measuring the diffusion (flow) of water in tissue: how fast and in what direction?
  • Isotropy (flows freely in any direction) vs. anisotropy (constained flow in only certain directions)
  • Water found most frequently in white matter of the brain.
  • Direction of flow ("fractional anisotrophy") can be color coded in DTI along the X, Y, & Z axis
  • Tractography: studying the different tracks of white matter fibers in the brain.
Images of DTI Studies
SLF in multiple views 
Connectome ModelThe Connectome
= the attempt to construct a comprehensive map of the neural connections in the brain. Connectome is parallel to the use of term "genome" for the full complement of human genes.

Problem of how detailed the connectome can be?
  • Microscale
  • Mesoscale
  • Macroscale


Large Scale Net
works in the Brain

Structural connections: anatomical links

  versus

Functional-Dynamic connections: actual interactions between neural elements in the brain


Yeo
                NetworksThe Functional Networks

There is some disagreement over how many major networks function in the brain. The list below indicate the 8 networks that most researchers have come to regard as most important.
  • Default Mode Network (DMN): sometimes called the "Task-Negative Network"
  • Salience Network (SALN)
  • Executive Control Network (ECN) or Fronto-Parietal Network [FPN]
  • Dorsal Attention Network (DAN)
  • Ventral Attention Network (VAN)
  • Auditory Network (AUDN)
  • Visual Network (VISN)
  • Motor-Tactile Network (MTN) or Somatosensory Network


Default Mode Network (DMN) ["Task-Negative Network"]

  • Discovered ca. 2001 by observing the patterns of oxygen use in brains during fMRI studies when participants were (1) actively doing something vs. (2) quietly "resting" in between tasks.
  • Distinctive pattern of action when the brain was "at rest"
  • Functions of the DMN
    • Spontaneous thinking (daydreaming)
    • Internally-directed thought; self-referential thought
    • Autobiographical self (episodic memory), reflecting on
    • Decision making about the future (recalling past & thinking ahead)
    • Mentalizing: Reflecting on what others are thinking & trying to understand their thoughts, feelings, intentions, etc.


 DMN Anatomy Development of DMN
  • The DMN develops across childhood into early adulthood
  • Damage/Dysfunction of DMN
    • ? possibly involved in Autism Spectrum Disorders
    • Hyperactive DMN is  associated with
      • schizophrenia (overly intensive self-reference; impairments in attention & working memory)
      • depression (negative rumination: constant dwelling on negative matters in thinking)

SALNSalience Network (SALN)
  • The SALN gives a person the ability to sift through the various external and internal stimuli and identify what is most important at that moment (= what is most salient).
  • This network integrates the various stimuli which come from the senses monitoring the outside world (visual, auditory, somatosensory, etc.) with the data that report what is happening within the individual's body (e.g., autonomic nervous system arousal, feelings of pleasure or pain, hunger, etc.).
  •  In doing so, the SALN signals when the person's behavior has to change, e.g., it's time to eat...to study...to run away from danger...to turn on a different television channel, etc.
  • The SALN is associated with the anterior cingulate cortex (ACC), presupplementary motor areas (preSMA), and the anterior insula (AI).

Executive Control Network (ECN) or Fronto-Parietal Network (FPN)

  • The  ECN/FPN deploys sustained attention and working memory to process the sensory-motor data it is receiving and both chooses to respond in a selective and particular way while suppressing responses which it finds irrelevant or erroneous.
  • Damage/dysfunction ==> "Dysexecutive Syndrome"
    • Cognitive problems with short and long-term memory; understanding how to deal with problems in dailylife; short attention span; cognitive flexibility
    • Emotional problems in speaking or responding inappropriately; anger, aggression, high levels of frustration
    • Behavioral problems of interacting with others socially, following social norms, etc.

Dorsal Attention Network (DAN): when we choose to pay attention to something

  • "Top-down" process of selecting or attending to important visual and spatial information; detecting new or novel features of the environment

Ventral Attention Network (VAN): when something around us suddenly grabs our attention
  • "Bottom-up" process that responds to unexpected or suddenly appearing stimuli in the environment; stimuli which "catch our attention" are monitored and acted upon by the VAN 

The three major sensory-motor networks involve

Auditory Network (AUDN)

Auditory Network

Visual Network (VISN)

Visual Network

Motor-Tactile Network (MTN; aka Sensory-Motor Network [SMN])

Motor-Tactile Network



This page was first posted February 25, 2016