The Rise of Homo sapiens: Introduction to the Brain

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

2. Introduction • 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? • Not technology or their physique • Perhaps their mental abilities

3. Introduction • 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

4. Introduction • 1st leap in cognition → 1.5 million years ago • 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 • “modern thinking” • Personal ornaments, art, elaborate rituals, scheduled hunting • Explained by enhancement in working memory capacity

5. The Brain • 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)

6. Brain Ontogeny • Cell proliferation: multiplication of cells • Until the 20th week • Migration: cells moving to their programmed location • Until the 29th week • Differentiation: developing a specific function • Continues until after birth • Apoptosis: cell death • Until the first 10 years

7. Brain Ontogeny • Left hemisphere • Language • Right hemisphere • Non-verbal & visual-spatial fuctions • Separated by a major fissure • Corpus callosum

8. Brain Ontogeny • Frontal lobe • Parietal lobe • Temporal lobe • Occipital lobe • Brodmann’s areas • Divides brain into 52 regions, based on cell type and function

9. Brain Ontogeny • Frontal lobe • Bordered by the lateral fissure and central sulcus • (Executive) functions: • Future planning • Decision-making • Problem-solving • Broca’s area • Damage • Broca’s aphasia • Personality changes

10. Brain Ontogeny • Frontal lobe (cont’d) • Cingulate cortex • 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

12. Brain Ontogeny • Parietal lobe • Posterior to the central sulcus • Function: visuospatial processing • Somatosensory cortex • Controls senses, especially touch • Damage: apraxia • Sub-regions: • Supramarginal gyrus: controls sensory discriminations • Angular gyrus: phonological storage

13. Brain Ontogeny • Temporal lobe • Inferior to the parietal lobe • Functions: language and speech interpretation, also important role in thinking, speech, visual processing, & memory • Sub-regions: • Superior temporal gyrus (Wernicke’s area) • Understanding of speech • Wernicke’s aphasia • Planum temporale: perception of pitch & harmony • Transverse temporal gyrus: primary auditory cortex

14. Brain Ontogeny • Sub-regions: • Inferior temporal gyrus • word & number recognition • Fusiform gyrus • Facial recognition • Damage: epilepsy due to anoxia

15. Brain Ontogeny • Occipital lobe • Posterior to parietal and temporal lobes • Functions: • Visual recognition and processing • Damage: blindness due to contra coup effect

17. Brain Ontogeny • Limbic system • Housed within the cortex and temporal lobe • Functions: processing of emotions & formation of memories • Main structures: • Hippocampus • Amygdala • Basal ganglia

18. Brain Ontogeny • 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

19. Brain Ontogeny • Amygdala • Anterior tips of hippocampus • Fear and rage responses • Amygdala → emotions → memory • Amygdalectomy → apathy

20. Brain Ontogeny • Basal ganglia • Collection of subcortical neurons • Function: control of movements • Substantia nigra • Manufacture of dopamine • Parkinson’s disease • Destruction of neurons → decreased dopamine • Hand, finger, foot tremors • Rigid muscles • Trouble walking

21. Brain Ontogeny • Treatments: • Levodopa (L-dopa) • Removal of globus pallidus • Deep brain stimulation • O.C.D. • Tourette’s syndrome

22. Other Subcortical Brain Structures • Cerebellum • 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

23. Other Subcortical Brain Structures • Brain stem • Lower brain structure • Pons • Receives sensory & motor output → cerebellum • Information crosses over to opposite side • Reticular formation • One of the oldest phylogenetic areas of the brain • Sleeping, eating, sex, also attention & motivation • Medulla • Controls vital functions: heart rate, breathing, & bp

24. Other Subcortical Brain Structures • Hypothalamus • 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

25. Handedness • 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

26. Handedness • 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

27. Ears and Hearing • Both ipsilateral and contralateral connections • Stronger contralateral connection • For example, right ear → left hemisphere (speech) • Left ear → right hemisphere → corpus callosum→ left hemisphere

28. Eyes and Vision • 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

30. Split-Brain Studies • Involves severing the corpus callosum in order to reduce seizures in severely epileptic patients • 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

31. Split-Brain Studies • Split-brain patients cannot repeat what they see in their left visual field • Left visual field → right half of each eye → right hemisphere • Hand & eye tasks • Will use their left hand to pick up what they saw in their right visual field (TREE) and vice versa

32. Split-Brain Studies • Left visual field Right visual field

33. Brain Myths • 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

34. Brain Myths • 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

35. Brain Myths • Myth #3A: The brain cannot regenerate its neurons. • There has been some evidence of neurogenesis in only the olfactory bulb and the hippocampus. • Myth #3B: The brain can regenerate its neurons. • People with massive brain damage usually do not get better. Quite often, they get much worse. Neurogenesis evidence is probably exaggerated.

36. Brain Myths • 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.

37. The End