The Rise of Homo sapiens: Chapters 1 & 2 Introductionand The Brain.

The Rise of Homo The Rise of Homo sapiens:sapiens:Chapters 1 & 2Chapters 1 & 2

IntroductionIntroduction

andand

The BrainThe Brain


Modern humans evolved in AfricaModern humans evolved in Africa ≈ ≈ 70,000 years ago → modern humans began to 70,000 years ago → modern humans began to

migratemigrate They eventually moved into Europe, where they They eventually moved into Europe, where they

shared the continent with Neanderthals for shared the continent with Neanderthals for several thousand years.several thousand years.

≈ ≈ 25,000 years ago, the last Neanderthal died.25,000 years ago, the last Neanderthal died. Ultimately, they became the only humans on Ultimately, they became the only humans on

Earth.Earth. What was the cause of their success?What was the cause of their success?

Not technology or their physiqueNot technology or their physique Perhaps their mental abilitiesPerhaps their mental abilities


Phineas Gage → tamping rod through Phineas Gage → tamping rod through frontal lobefrontal lobe Before accident-- responsible, dependable, Before accident-- responsible, dependable,

smart business mansmart business man After-- capricious, profane, irritableAfter-- capricious, profane, irritable Dr.– “…persistent in executing all his Dr.– “…persistent in executing all his

plans of operation.”plans of operation.” Executive functions: making decisions, Executive functions: making decisions,

forming goals, planning ahead, ability to forming goals, planning ahead, ability to change plans change plans

IntroductionIntroduction 11stst leap in cognition → 1.5 million years ago leap in cognition → 1.5 million years ago

Evolution of Evolution of Homo erectusHomo erectus Movement away from safe, wooded habitatsMovement away from safe, wooded habitats Changes in social life and landscape useChanges in social life and landscape use

Perhaps facilitated by physiological changes in sleep Perhaps facilitated by physiological changes in sleep patternspatterns

22ndnd leap in cognition → 100,000 – 40,000 years ago leap in cognition → 100,000 – 40,000 years ago ““modern thinking”modern thinking” Personal ornaments, art, elaborate rituals, scheduled Personal ornaments, art, elaborate rituals, scheduled

huntinghunting Explained by enhancement in working memory capacityExplained by enhancement in working memory capacity

The BrainThe Brain

Edwin Smith papyrusEdwin Smith papyrus Earliest written evidence about the brain Earliest written evidence about the brain

& behavior& behavior ≈ ≈ 2700 BCE (Origin is a mystery)2700 BCE (Origin is a mystery) First known use of the term “brain”First known use of the term “brain” Broca’s aphasiaBroca’s aphasia Internal head injury (localization)Internal head injury (localization)

Brain OntogenyBrain Ontogeny

Cell proliferationCell proliferation: multiplication of cells: multiplication of cells Until the 20Until the 20thth week week

MigrationMigration: cells moving to their : cells moving to their programmed locationprogrammed location Until the 29Until the 29thth week week

DifferentiationDifferentiation: developing a specific : developing a specific functionfunction Continues until after birthContinues until after birth

ApoptosisApoptosis: cell death: cell death Until the first 10 yearsUntil the first 10 years


Left hemisphereLeft hemisphere LanguageLanguage

Right hemisphereRight hemisphere Non-verbal & Non-verbal &

visual-spatial visual-spatial fuctionsfuctions

Separated by a Separated by a major fissuremajor fissure

Corpus callosumCorpus callosum


Frontal lobeFrontal lobe Parietal lobeParietal lobe Temporal lobeTemporal lobe Occipital lobeOccipital lobe

Brodmann’s areasBrodmann’s areas Divides brain into Divides brain into

52 regions, based 52 regions, based on cell type and on cell type and functionfunction


Frontal lobeFrontal lobe Bordered by the lateral fissure and Bordered by the lateral fissure and

central sulcuscentral sulcus (Executive) functions: (Executive) functions:

Future planningFuture planning Decision-makingDecision-making Problem-solvingProblem-solving

Broca’s areaBroca’s area DamageDamage

Broca’s aphasiaBroca’s aphasia Personality changesPersonality changes


Frontal lobe (cont’d)Frontal lobe (cont’d) Cingulate cortexCingulate cortex

Attention, especially short- and long-term goalsAttention, especially short- and long-term goals Prefrontal cortexPrefrontal cortex

Dorsolateral prefrontal cortexDorsolateral prefrontal cortex: selective : selective attention, task organization, planning, flexibilityattention, task organization, planning, flexibility

OrbitofrontalOrbitofrontal: processing of emotions, decision-: processing of emotions, decision-making in social interactionsmaking in social interactions

VentromedialVentromedial: central part of the orbitofrontal : central part of the orbitofrontal cortex, located in the middle of the braincortex, located in the middle of the brain

Brain OntogenyBrain Ontogeny Parietal lobeParietal lobe

Posterior to the central sulcusPosterior to the central sulcus Function: visuospatial processingFunction: visuospatial processing Somatosensory cortexSomatosensory cortex

Controls senses, especially touchControls senses, especially touch Damage: apraxiaDamage: apraxia Sub-regions:Sub-regions:

Supramarginal gyrus: controls sensory Supramarginal gyrus: controls sensory discriminationsdiscriminations

Angular gyrus: phonological storageAngular gyrus: phonological storage


Temporal lobeTemporal lobe Inferior to the parietal lobeInferior to the parietal lobe Functions: language and speech Functions: language and speech

interpretation, also important role in interpretation, also important role in thinking, speech, visual processing, & thinking, speech, visual processing, & memorymemory

Sub-regions:Sub-regions: Superior temporal gyrus (Wernicke’s area)Superior temporal gyrus (Wernicke’s area)

Understanding of speechUnderstanding of speech Wernicke’s aphasiaWernicke’s aphasia Planum temporale: perception of pitch & harmonyPlanum temporale: perception of pitch & harmony Transverse temporal gyrus: primary auditory cortex Transverse temporal gyrus: primary auditory cortex


Sub-regions:Sub-regions: Inferior temporal gyrusInferior temporal gyrus

word & number recognitionword & number recognition Fusiform gyrusFusiform gyrus

Facial recognitionFacial recognition

Damage: epilepsy due to anoxiaDamage: epilepsy due to anoxia

Brain OntogenyBrain Ontogeny Occipital lobeOccipital lobe

Posterior to parietal and temporal lobesPosterior to parietal and temporal lobes Functions:Functions:

Visual recognition and processingVisual recognition and processing Damage: blindness due to contra coup effectDamage: blindness due to contra coup effect


Limbic systemLimbic system Housed within the cortex and temporal Housed within the cortex and temporal

lobelobe Functions: processing of emotions & Functions: processing of emotions &

formation of memoriesformation of memories Main structures:Main structures:

HippocampusHippocampus AmygdalaAmygdala Basal gangliaBasal ganglia


HippocampusHippocampus H.M., suffered frequent grand mal H.M., suffered frequent grand mal

seizuresseizures Underwent hippocampectomy & Underwent hippocampectomy &

amygdalectomyamygdalectomy Led to inability to recognize faces, Led to inability to recognize faces,

retrograde and anterograde amnesiaretrograde and anterograde amnesia Declarative memory impairedDeclarative memory impaired Procedural memory intactProcedural memory intact


AmygdalaAmygdala Anterior tips of Anterior tips of

hippocampushippocampus Fear and rage Fear and rage

responsesresponses Amygdala → Amygdala →

emotions → emotions → memorymemory

Amygdalectomy → Amygdalectomy → apathyapathy


Basal gangliaBasal ganglia Collection of subcortical neuronsCollection of subcortical neurons Function: control of movementsFunction: control of movements Substantia nigraSubstantia nigra

Manufacture of dopamineManufacture of dopamine Parkinson’s diseaseParkinson’s disease

Destruction of neurons → decreased dopamineDestruction of neurons → decreased dopamine Hand, finger, foot tremorsHand, finger, foot tremors Rigid musclesRigid muscles Trouble walkingTrouble walking

Brain OntogenyBrain Ontogeny Treatments:Treatments:

Levodopa (L-dopa)Levodopa (L-dopa) Removal of globus pallidusRemoval of globus pallidus Deep brain stimulationDeep brain stimulation

O.C.D.O.C.D. Tourette’s syndromeTourette’s syndrome

Other Subcortical Brain Other Subcortical Brain StructuresStructures

CerebellumCerebellum Very old brain structureVery old brain structure Rapid expansion in Rapid expansion in

modern humansmodern humans Functions: integration Functions: integration

of sensory perception of sensory perception and motor output & and motor output & control of fine motor control of fine motor movementsmovements

Lesions/damage → Lesions/damage → difficulties in difficulties in equilibrium, balance, equilibrium, balance, and postureand posture


Brain stemBrain stem Lower brain structureLower brain structure PonsPons

Receives sensory & motor output → cerebellumReceives sensory & motor output → cerebellum Information crosses over to opposite sideInformation crosses over to opposite side

Reticular formationReticular formation One of the oldest phylogenetic areas of the brainOne of the oldest phylogenetic areas of the brain Sleeping, eating, sex, also attention & motivationSleeping, eating, sex, also attention & motivation

MedullaMedulla Controls vital functions: heart rate, breathing, & Controls vital functions: heart rate, breathing, &

bpbp


HypothalamusHypothalamus Regulates the autonomic nervous Regulates the autonomic nervous

system, the endocrine & hormonal system, the endocrine & hormonal systems, and the body’s general systems, and the body’s general homeostasishomeostasis

ThalamusThalamus Top of spinal cordTop of spinal cord Relay station for sensory informationRelay station for sensory information Also regulates attentionAlso regulates attention

HandednessHandedness

Both ipsilateral (same-side) and Both ipsilateral (same-side) and contralateral (opposite-side) connections contralateral (opposite-side) connections to the two cerebral hemispheresto the two cerebral hemispheres

Stronger contralateral connectionStronger contralateral connection 90-95% → right-handed90-95% → right-handed 5-10% → left-handed or non-right-handed5-10% → left-handed or non-right-handed Right-handed and most non-right-handed Right-handed and most non-right-handed

people have speech located in left people have speech located in left hemispherehemisphere

HandednessHandedness

Many animals also have vocalization Many animals also have vocalization ability located in the left hemisphere.ability located in the left hemisphere.

Homo habilisHomo habilis (≈ 2 million years ago) (≈ 2 million years ago) → enlarged Broca’s area (→ enlarged Broca’s area (leftleft hemisphere; speech production) but hemisphere; speech production) but not earlier australopithecinesnot earlier australopithecines

Toth (1985) examined stone tools Toth (1985) examined stone tools from 1.4 – 1.9 million years ago → from 1.4 – 1.9 million years ago → more right-handersmore right-handers

Ears and HearingEars and Hearing

Both ipsilateral and contralateral connectionsBoth ipsilateral and contralateral connections Stronger contralateral connectionStronger contralateral connection For example, right ear → left hemisphere (speech)For example, right ear → left hemisphere (speech)

Left ear → right hemisphere → corpus callosum→ left Left ear → right hemisphere → corpus callosum→ left hemispherehemisphere

Eyes and VisionEyes and Vision

Each eye is connected to both Each eye is connected to both hemisphereshemispheres

Ipsilateral and contralateral connections Ipsilateral and contralateral connections are equalare equal

Left half of each eye → left hemisphere Left half of each eye → left hemisphere & views the right visual field& views the right visual field

Right half of each eye → right Right half of each eye → right hemisphere & views the left visual fieldhemisphere & views the left visual field

Split-Brain StudiesSplit-Brain Studies

Involves severing the corpus Involves severing the corpus callosum in order to reduce seizures callosum in order to reduce seizures in severely epileptic patientsin severely epileptic patients

Split-brain patients cannot repeat Split-brain patients cannot repeat something they’ve heard in their left something they’ve heard in their left ear because the knowledge cannot ear because the knowledge cannot travel across the travel across the corpus callosumcorpus callosum to to be processed in the left hemispherebe processed in the left hemisphere


Split-brain patients cannot repeat Split-brain patients cannot repeat what they see in their left visual fieldwhat they see in their left visual field Left visual field → right half of each eye Left visual field → right half of each eye

→ right hemisphere→ right hemisphere Hand & eye tasksHand & eye tasks

Will use their left hand to pick up what Will use their left hand to pick up what they saw in their right visual field they saw in their right visual field (TREE) and vice versa(TREE) and vice versa


Left visual fieldLeft visual field Right Right visual fieldvisual field

Brain MythsBrain Myths

Myth #1: We only use 10% of our Myth #1: We only use 10% of our brains.brains. Cannot be measured (walking, sitting, Cannot be measured (walking, sitting,

moving, etc.)moving, etc.) Vincent et al. (2007) – found cortical Vincent et al. (2007) – found cortical

activation in unconscious monkeysactivation in unconscious monkeys May have been created to motivateMay have been created to motivate


Myth #2: Alcohol destroys brain cells.Myth #2: Alcohol destroys brain cells. Little or no evidence for moderate Little or no evidence for moderate

drinkers with adequate dietsdrinkers with adequate diets However, severe and long-term However, severe and long-term

alcoholism is associated with Korsakoff’s alcoholism is associated with Korsakoff’s syndrome → memory problemssyndrome → memory problems


Myth #3A: The brain cannot regenerate its Myth #3A: The brain cannot regenerate its neurons.neurons. There has been some evidence of neurogenesis There has been some evidence of neurogenesis

in only the olfactory bulb and the hippocampus.in only the olfactory bulb and the hippocampus.

Myth #3B: The brain can regenerate its Myth #3B: The brain can regenerate its neurons.neurons. People with massive brain damage usually do People with massive brain damage usually do

not get better. Quite often, they get much not get better. Quite often, they get much worse. Neurogenesis evidence is probably worse. Neurogenesis evidence is probably exaggerated.exaggerated.


Myth #4: Gay men’s and lesbians’ brains Myth #4: Gay men’s and lesbians’ brains are different from heterosexuals’ brains.are different from heterosexuals’ brains. Not much evidence for either side.Not much evidence for either side. Some evidence for neuronal organization Some evidence for neuronal organization

differences in the hippocampus of gay men differences in the hippocampus of gay men but this has not shown any cognitive but this has not shown any cognitive consequence whatsoever.consequence whatsoever.

TheTheEndEnd

The Rise of Homo sapiens: Chapters 1 & 2 Introductionand The Brain.

Documents