Brain Mapping Techniques

Recent Brain Mapping Techniques

• Brain mapping techniques have revealed insights into cortical networks.
• Sophisticated noninvasive stimulation and recording techniques have been developed since the late 1970s.
• These techniques measure brain activity related to behavior, including:
  • Electroencephalography (EEG)
  • Event-related potential (ERP)
  • Metabolic (PET)
  • Vascular (magnetic resonance imaging [MRI], fMRI)
• Cognitive neuroscience is a new field studying the neural bases of cognition.
• Cognitive neuroscientists use imaging to map the human brain.
• Social psychologists and neuroscientists utilize imaging to explore brain-mediated social interactions.
• Economists utilize imaging to discover how the brain makes decisions.

The Cerebellum's Role

• The human cerebellum contains 80% of the brain's neurons.
• The cerebellum plays a central role in motor control and motor learning.
• The cerebellum plays a role in cognitive processes.
• Neocortex-cerebellum interconnections involve the prefrontal cortex, Broca's area, and neocortical regions.
• The cerebellum produces fine movements and perception.
• The cerebellum is associated with working memory, attention, language, music, social/emotional processing, mood, and decision-making.
• Rs-fMRI has identified cerebellar networks related to similar cortical networks.

Brain Mediation of Social Interactions and Social Neuroscience

• Social neuroscience combines cognitive neuroscience tools with social psychology constructs.
• It seeks to understand how the brain mediates social interactions.
• Theory of mind (ToM) is the attribution of mental states to others.
• ToM includes the understanding that others have different feelings and beliefs.
• The capacity to understand others can be inferred from empathy.
• fMRI studies show a dissociable network for theory of mind.
• Affective (empathy) and cognitive (ToM) systems are separate routes used to understand others.
• Brain activity increases in the right lateral prefrontal cortex and lateral parietal cortex upon recognizing your own face.
• Increased brain activity in the medial prefrontal regions occurs when determining if trait words/sentences are self-descriptive.
• Social cognitions are associated with activation in the medial prefrontal (mPFC) and TPJ regions.
• During rest, mPFC-TPJ activity, along with activity in the default network, commits new social information to memory.
• High default network activity correlates with superior social cognition and social memory.

Goals of Neuroeconomics

• Neuroeconomics combines economics, psychology, and neuroscience.
• It explains decision-making processes using brain activity patterns.
• Two neural decision pathways influence choices:
  • Deliberate, slow, rule-driven, emotionally neutral reflective system
  • Fast, automatic, emotionally biased reflexive system
• Widespread activity appears in the dopaminergic reward system during quick decisions for immediate gains:
  • Ventromedial prefrontal cortex
  • Ventral striatum (nucleus accumbens)
• Slower, deliberative decisions activate the lateral prefrontal, medial temporal, and posterior parietal cortex.
• Neuroeconomists aim to identify neural activity patterns in decision-making.
• Epigenetic factors contribute to the balance between reflective and reflexive systems.

Clinical Neuropsychological Assessment

• It is the systematic evaluation of cognitive function in individuals with neurological or psychological impairment.
• It now plays a key role in rehabilitation for chronic diseases, after functional imaging advancements.
• Variability in cognitive effects of neurological disease is due variance in individual brains and because brain function varies per individual.
• Cognitive functions are influenced by, the nature of brain dysfunction and psychological/socioenvironmental factors like personality, culture, and relationships.
• Assessments must consider a person's holistic life context.
• Neuropsychological assessment evolved after WWII as investigators studied brain injuries in soldiers.
• Broad standardized test batteries and paper-and-pencil tests were developed assessing cognition, memory, and spatial skills.
• Test batteries have remained static for 30 years.(Bilder & Reise, 2019)
• CANTAB (Cambridge Neuropsychological Test Battery) was developed in the 1990s which can be administered via touch screen.
• The CANTAB has led to the development of 20 computerized batteries integrated with neuroimaging (MRI, fMRI, and EEG).
• Computerized batteries allow voice and facial expression assessment for information that regular tests can not account for.
• Computerized batteries allow scores to be compared against thousands across all different psychosocial backgrounds, (ethnicity, race, education, and gender).
• Computer-generated data analysis supplements trained neuropsychologists, it doesn't replace them.

Mapping the Brain

• Mapping the human brain connectome is a major scientific challenge.
• The NIH awarded $40 million to researchers for mapping structural and functional fiber pathway connections in the living human brain
• The Human Connectome Project (HCP) combines diffusion tensor imaging (DTI) and functional connectivity magnetic resonance imaging (fcMRI).
• HCP investigators scanned 1200 healthy adults’ brains, including 300 twin pairs (by 2016).
• One study in the UK aims to scan 100,000 participants (Elam et al., 2021).
• The first step in HCP mapping was identifying the parcellation of the cerebral cortex.
• Brain maps have been constructed for over 100 years. There are 50-200 distinct areas, depending on the analysis method.
• The HCP used a machine learning classifier of >500 brains to parcel the cortex into 180 detectable areas in ~97% participants (Glasser et al., 2016).
• This parcellation is more complex than Brodmann's cytoarchitectonic map but derives from his basic organization.
• Specific processes and disorders are described using mapping technology.
• Age-related brain changes are an important topic as life spans increase.
• Functional connectivity decreases with age, but some networks (default network) increase in connectivity.
• Increased connectivity may help to maintain healthy cognitive function as people age (Podgórski et al., 2021).
• Functional connectivity MRI (fcMRI) measures intrinsic functional correlations between brain regions using resting-state fMRI (rsfMRI).
• Consistent connectivity patterns, or nerve tracts, in the brain were found when pooling fcMRI on thousands of healthy young adults.
• Thomas Yeo and colleagues (2011) parcellated the human cerebral cortex into 17 networks using fcMRI data from 1000 participants.
• The cerebral cortex consists of primary sensory and motor networks, as well as multiple large-scale networks that form the association cortex.
• Adjacent areas in the sensory and motor networks are largely local showing strong functional coupling.
• Turquoise and blue/gray regions in the somatosensory and motor cortices and purple region in the visual cortex illustrate couplings.
• Association networks include areas across the prefrontal, parietal, anterior temporal, and midline regions.
• Distributed yellow regions show prefrontal-posterior parietal connectivity.
• Light red areas include the temporal, posterior parietal, and prefrontal regions.
• A large number of cortical regions are functionally connected into four distinct social networks.
• Other networks are related to functions such as memory, space, and vision.
• The default network involves regions of the frontal and parietal lobes.
• The default network is not a single network, but rather two parallel networks including adjacent dorsal and ventral components (Braga et al., 2019).
• Higher-resolution imaging functionally dissociates these components (Sangil Lee et al., 2021).
• fMRI studies show that the ventral region responds to the vividness of the imagined events and the dorsal region responds to their valence.

Tractography

• Diffusion Tensor Imaging (DTI) studies provide results that compliment the networks mapped by fcMRI.
• Tractography measures actual neuroanatomical pathways for specific traits.
• Tract tracing was traditionally performed postmortem on single brains.
• Tractography can be performed quickly on measurements made simultaneously in the entire brain.
• This allows researchers to correlate behavioral traits with connectivity patterns.
• Psyche Loui and colleagues (2011) studied the neural basis of perfect (absolute) pitch.
• Perfect pitch is the ability to not only discriminate among musical notes but also to name any note heard.
• Perfect pitch is rare, but shared by people with remarkable talents such as mozart.
• Perfect pitch development is sensitive to early experiences, including language.
• Loui's matched musicians with and without absolute pitch for gender, age, handedness, ethnicity, IQ score, and years of musical training.
• Participants were given a pitch-labeling test that placed musicians with absolute pitch into more or less accurate categories.
• Those less accurate were found to be superior when compared to participants without absolute pitch.
• Researchers hypothesized absolute pitch correlates to increased connectivity in brain regions that process sounds.
• They used DTI to reconstruct white-matter tracts connecting two temporal cortex regions (superior and middle temporal gyri) as well as the corticospinal tract.
• Absolute pitch individuals have greater connectivity in temporal lobe regions responsible for pitch perception.
• The effect is highest in those with higher accuracy.
• Left-hemisphere tract volume was the only predictor when correlated to performance on a test of perfect pitch with volume.
• Hyperconnectivity in the left hemisphere is responsible for absolute pitch.
• Other exceptional talents may be related to hyperconnectivity in cerebral regions.
• Connectivity between auditory regions in the superior temporal gyrus and emotional processing in the medial prefrontal cortex and insula, can explain individual differences in reward sensitivity to music ,(Matthew sachs et al 2016).
• Reduced structural and functional connectivity can be related to cognitive impairments from brain injuries, neurodevelopmental/psychiatric disorders, and degeneration.

Social Cognition and the Brain

• Our understanding of ourselves and social interactions are linked.
• Attitudes and beliefs about ourselves and others are part of this.
• Expressing attitudes activates the prefrontal, anterior cingulate, and temporoparietal junction (TPJ) regions.
• Social cognitions correlate with activation of brain regions, especially the medial prefrontal (mPFC) and TPJ regions.
• mPFC-TPJ activity produces social cognitions.
• Lieberman and Eisenberger's review of 10,000 fMRI studies concluded the anterior cingulate cortex relates to pain processing.
• Frontal lobe development extends up to age 30
• Expectations about a stimulus can alter the actual feeling of an event.
• Expecting pain increases activity the anterior cingulate cortex.
• Self-regulation is the ability to control emotions and impulses.
• Prefrontal regions are critical in self-regulation.
• A uniquely human ability of self-regulation: is putting feelings into words.
• Verbal labeling associates with increased activity in the right lateral prefrontal regions.