Download Brain Ontogeny

The Rise of Homo
sapiens:
Chapters 1 & 2
Introduction
and
The Brain
Introduction
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Modern humans evolved in Africa
≈ 70,000 years ago → modern humans began to migrate
They eventually moved into Europe, where they shared
the continent with Neanderthals for several thousand
years.
≈ 25,000 years ago, the last Neanderthal died.
Ultimately, they became the only humans on Earth.
What was the cause of their success?
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Not technology or their physique
Perhaps their mental abilities
Introduction
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Phineas Gage → tamping rod through frontal lobe
Before accident-- responsible, dependable, smart
business man
 After-- capricious, profane, irritable
 Dr.– “…persistent in executing all his plans of
operation.”
 Executive functions: making decisions, forming goals,
planning ahead, ability to change plans
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Introduction
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1st leap in cognition → 1.5 million years ago
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Evolution of Homo erectus
 Movement away from safe, wooded habitats
 Changes in social life and landscape use
Perhaps facilitated by physiological changes in sleep patterns
2nd leap in cognition → 100,000 – 40,000 years ago
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“modern thinking”
Personal ornaments, art, elaborate rituals, scheduled hunting
Explained by enhancement in working memory capacity
The Brain
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Edwin Smith papyrus
Earliest written evidence about the brain & behavior
 ≈ 2700 BCE (Origin is a mystery)
 First known use of the term “brain”
 Broca’s aphasia
 Internal head injury (localization)
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Brain Ontogeny
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Cell proliferation: multiplication of cells
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Migration: cells moving to their programmed
location
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Until the 29th week
Differentiation: developing a specific function
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Until the 20th week
Continues until after birth
Apoptosis: cell death
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Until the first 10 years
Brain Ontogeny
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Left hemisphere
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Right hemisphere
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Language
Non-verbal & visualspatial fuctions
Separated by a major
fissure
Corpus callosum
Brain Ontogeny
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Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
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Brodmann’s areas
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Divides brain into 52
regions, based on cell type
and function
Brain Ontogeny
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Frontal lobe
Bordered by the lateral fissure and central sulcus
 (Executive) functions:
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Future planning
 Decision-making
 Problem-solving
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Broca’s area
 Damage
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Broca’s aphasia
 Personality changes
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Brain Ontogeny
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Frontal lobe (cont’d)
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Cingulate cortex
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Attention, especially short- and long-term goals
Prefrontal cortex
Dorsolateral prefrontal cortex: selective attention, task
organization, planning, flexibility
 Orbitofrontal: processing of emotions, decision-making
in social interactions
 Ventromedial: central part of the orbitofrontal cortex,
located in the middle of the brain
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Brain Ontogeny
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Parietal lobe
Posterior to the central sulcus
 Function: visuospatial processing
 Somatosensory cortex
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Controls senses, especially touch
Damage: apraxia
 Sub-regions:
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Supramarginal gyrus: controls sensory discriminations
 Angular gyrus: phonological storage
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Brain Ontogeny
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Temporal lobe
Inferior to the parietal lobe
 Functions: language and speech interpretation, also
important role in thinking, speech, visual processing,
& memory
 Sub-regions:
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Superior temporal gyrus (Wernicke’s area)
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Understanding of speech
Wernicke’s aphasia
Planum temporale: perception of pitch & harmony
Transverse temporal gyrus: primary auditory cortex
Brain Ontogeny
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Sub-regions:
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Inferior temporal gyrus
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word & number recognition
Fusiform gyrus
 Facial recognition
Damage: epilepsy due to anoxia
Brain Ontogeny
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Occipital lobe
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Posterior to parietal and temporal lobes
Functions:
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Visual recognition and processing
Damage: blindness due to contra coup effect
Brain Ontogeny
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Limbic system
Housed within the cortex and temporal lobe
 Functions: processing of emotions & formation of
memories
 Main structures:
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Hippocampus
 Amygdala
 Basal ganglia
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Brain Ontogeny
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Hippocampus
H.M., suffered frequent grand mal seizures
 Underwent hippocampectomy & amygdalectomy
 Led to inability to recognize faces, retrograde and
anterograde amnesia
 Declarative memory impaired
 Procedural memory intact
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Brain Ontogeny
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Amygdala
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Anterior tips of
hippocampus
Fear and rage responses
Amygdala → emotions →
memory
Amygdalectomy →
apathy
Brain Ontogeny
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Basal ganglia
Collection of subcortical neurons
 Function: control of movements
 Substantia nigra
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Manufacture of dopamine
 Parkinson’s disease
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Destruction of neurons → decreased dopamine
Hand, finger, foot tremors
Rigid muscles
Trouble walking
Brain Ontogeny
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Treatments:
 Levodopa (L-dopa)
 Removal of globus pallidus
 Deep brain stimulation
O.C.D.
 Tourette’s syndrome
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Other Subcortical Brain Structures
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Cerebellum
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Very old brain structure
Rapid expansion in
modern humans
Functions: integration of
sensory perception and
motor output & control
of fine motor movements
Lesions/damage →
difficulties in equilibrium,
balance, and posture
Other Subcortical Brain Structures
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Brain stem
Lower brain structure
 Pons
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Receives sensory & motor output → cerebellum
 Information crosses over to opposite side
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Reticular formation
One of the oldest phylogenetic areas of the brain
 Sleeping, eating, sex, also attention & motivation
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Medulla
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Controls vital functions: heart rate, breathing, & bp
Other Subcortical Brain Structures
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Hypothalamus
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Regulates the autonomic nervous system, the
endocrine & hormonal systems, and the body’s
general homeostasis
Thalamus
Top of spinal cord
 Relay station for sensory information
 Also regulates attention
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Handedness
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Both ipsilateral (same-side) and contralateral
(opposite-side) connections to the two cerebral
hemispheres
Stronger contralateral connection
90-95% → right-handed
5-10% → left-handed or non-right-handed
Right-handed and most non-right-handed
people have speech located in left hemisphere
Handedness
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Many animals also have vocalization ability
located in the left hemisphere.
Homo habilis (≈ 2 million years ago) → enlarged
Broca’s area (left hemisphere; speech production)
but not earlier australopithecines
Toth (1985) examined stone tools from 1.4 – 1.9
million years ago → more right-handers
Ears and Hearing
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Both ipsilateral and contralateral connections
Stronger contralateral connection
For example, right ear → left hemisphere (speech)
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Left ear → right hemisphere → corpus callosum→ left hemisphere
Eyes and Vision
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Each eye is connected to both hemispheres
Ipsilateral and contralateral connections are equal
Left half of each eye → left hemisphere & views
the right visual field
Right half of each eye → right hemisphere &
views the left visual field
Split-Brain Studies
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Involves severing the corpus callosum in order
to reduce seizures in severely epileptic patients
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Split-brain patients cannot repeat something
they’ve heard in their left ear because the
knowledge cannot travel across the corpus
callosum to be processed in the left hemisphere
Split-Brain Studies
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Split-brain patients cannot repeat what they see
in their left visual field
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Left visual field → right half of each eye → right
hemisphere
Hand & eye tasks
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Will use their left hand to pick up what they saw in
their right visual field (TREE) and vice versa
Split-Brain Studies
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Left visual field
Right visual field
Brain Myths
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Myth #1: We only use 10% of our brains.
Cannot be measured (walking, sitting, moving, etc.)
 Vincent et al. (2007) – found cortical activation in
unconscious monkeys
 May have been created to motivate
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Brain Myths
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Myth #2: Alcohol destroys brain cells.
Little or no evidence for moderate drinkers with
adequate diets
 However, severe and long-term alcoholism is
associated with Korsakoff ’s syndrome → memory
problems
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Brain Myths
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Myth #3A: The brain cannot regenerate its neurons.
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There has been some evidence of neurogenesis in only
the olfactory bulb and the hippocampus.
Myth #3B: The brain can regenerate its neurons.
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People with massive brain damage usually do not get
better. Quite often, they get much worse. Neurogenesis
evidence is probably exaggerated.
Brain Myths
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Myth #4: Gay men’s and lesbians’ brains are different
from heterosexuals’ brains.
Not much evidence for either side.
 Some evidence for neuronal organization differences
in the hippocampus of gay men but this has not
shown any cognitive consequence whatsoever.
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The
End