Brain and Self

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Introduction to Neuroscience: The Brain and Self

Overview

  • The brain constructs a sense of self and body image.
  • The superior parietal lobule (SPL) plays a crucial role in spatial navigation and body awareness.
  • Damage to SPL can result in conditions where patients feel their limbs belong to someone else.
  • Neuroscience of self includes studies on body image, agency, and ownership.

How the Brain Creates a Sense of Self

  • The feeling of being anchored in one’s body is a brain-generated construct.
  • The superior parietal lobule (SPL) is responsible for spatial awareness and body perception.
  • Henry Head and Lord Russell Brain coined the term “body image.”
  • Right hemisphere is primarily involved in body image perception.

Effects of SPL Damage

  • Stroke in SPL can lead to somatoparaphrenia, where patients deny ownership of their limb.
  • Patients may claim their arm belongs to someone else.
  • The brain fills in incongruencies with fabricated explanations.

Apotemnophilia (Xenomelia)

  • Some individuals have an intense desire to amputate a healthy limb.
  • The postcentral gyrus (S1, S2, S3) processes sensory information from body parts.
  • Superior parietal lobule (SPL) provides an abstract sense of self.
  • Brain imaging shows missing representation of the limb in SPL, causing a sense of detachment.
  • Patients report relief and happiness post-amputation.

Neuroscience of Self-Other Distinction

  • The temporal parietal junction (TPJ) integrates sensory inputs to define self vs. others.
  • Damage to TPJ can lead to out-of-body experiences or a blurring of self-other distinction.
  • TPJ deactivates during REM sleep, contributing to dream states where body identity shifts.

Experiments on Body Perception

  • Rubber Hand Illusion:
  • Participants feel ownership of a rubber hand if synchronized stroking occurs.
  • OCD and Contamination Experiment:
  • Watching someone touch a contaminant can induce disgust in the observer.
  • Watching someone wash hands can provide relief.
  • The insula processes disgust and internal bodily sensations.

Neuroscience of Attention

  • Orbitofrontal cortex filters sensory information, determining vigilance levels.
  • Hyperactivity in orbitofrontal cortex is linked to OCD and compulsive behaviors.
  • Prefrontal cortex serves as the “brake system” for controlling impulses and maintaining rational thought.

Brain Damage and Attention Disorders

  • Self-inflicted brain damage (case study): A man with severe OCD shot his orbitofrontal cortex and was cured of OCD.
  • Electrode implantation can activate dormant neurons to restore function in conditions like Parkinson’s.
  • L-Dopa treatment provides dopamine but struggles with blood-brain barrier penetration.

Techniques to Study the Brain

  • EEG (Electroencephalogram): Measures electrical activity and brain waves.
  • CT Scan: Provides x-ray images of the brain.
  • MRI (Magnetic Resonance Imaging): Uses hydrogen waves to image brain structures.
  • PET Scan: Tracks glucose-like substances to monitor receptor activity.
  • fMRI (Functional MRI): Measures oxygen and blood flow to track brain activity.

Neuroscience of Vision and Perception

  • Vision is processed in the occipital lobes (V1, MT, Fusiform Gyrus).
  • Blindsight: A condition where individuals can navigate obstacles despite cortical blindness.
  • Emotional vision: Direct pathways from the visual cortex to the amygdala allow fast emotional reactions before object recognition.

Top-Down vs. Bottom-Up Processing

  • Bottom-Up: Sensory input processed step by step.
  • Top-Down: Brain fills in gaps based on past experiences and expectations.
  • Charles Bonnet Syndrome: Hallucinations occur when sensory input is degraded and the brain “fills in” missing visual data.

Vestibular System and Body Image

  • The vestibular system in the inner ear provides balance and body orientation.
  • Damage to vestibular system can result in distorted body perception and floating sensations.
  • Sleep paralysis and body hallucinations result from disrupted vestibular feedback.

Conclusion

  • Body image, self-perception, and agency are all constructs of the brain.
  • Self-experiences are fluid, influenced by brain activity, damage, and perception.
  • The next lecture will explore Principles of Neuroplasticity and how the brain adapts to change.
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