COGNITIVE SCIENCE 17

What’s A Brain?

Part 1

Jaime A. Pineda, Ph.D.

Meshberger, JAMA 264:1837-1841

The Fundamental Circularity of Being

“The world is inseparable from the subject, but from a subject which is nothing but a projection of the world,and the subject is inseparable from the world, but froma world which the subject itself projects.”

Merleau-Ponty (1906-1961)

Mind-Body Question

• Dualism– Belief in the dual

nature of reality– Mind and body are

separate– Body is made of

ordinary matter– Mind is not

• Monism– Belief that everything

in the universe consists of matter and energy

– Mind is a phenomenon produced by the workings of the nervous system

The goal of Cognitive Neuroscience is to provide andexplain the mapping between

brain and mind

Or put another way, between

structure and function

Is there an identity such that brain=mind?Is it more of a correspondence?Just what is the relationship?

BODY-MIND RELATIONSHIP(STRUCTURE-FUNCTION)

• BODY/BRAIN • MIND MemoryAttentionLanguagePlanningCreativityAwarenessConsciousness

Classical physics

BODY-MIND RELATIONSHIP(STRUCTURE-FUNCTION)

• BODY/BRAIN • MIND MemoryAttentionLanguagePlanningCreativityAwarenessConsciousness

Self-directed neural plasticity?Quantum physics and the causal efficacy of thought?

Is Reality a “Construction”?

Stimulus Selection InterpretationBottom-up processing Top-down processing

Rene Descartes (1596-1650)

De Homine – 1662

Mechanistic view of brain

Pineal gland – gateway to soul

“…ingenuity and originality were unfortunately based onpure speculation and incorrectanatomical observations.”

“I think therefore I am”

Luigi Galvani

(1737-1798)

Professor of Obstetrics

Moves frog leg with static electricity

Detects electricity in the nerves offrogs

Bell –Magendi Law 1811

Paul Broca(1824-1880)

Anthropologist and anatomist

Paris educated MD pathologist

“Tan” aphasic patient died inApril 1861

“Nous parlons avez l’hemispheregauche”

(We speak with the left hemisphere)

Franz Joseph Gall (1758-1828)

Analysis of the shapes and lumps of the skull would reveal a person’s personality and intellect.

Phrenology

Modern Phrenology

Unilateral Neglect

- lesions to right parietal cortex - failure to notice things on the left side- failure to remember things on the left side

Split Brain

Neurons• Functional units of

communication• 100 billion + a few million• Independent units (Neuron

Doctrine)• Bioelectrically driven

(Functional polarity)• Categorized in terms of

Function (sensory, motor); Location (cortical, spinal); NT (cholinergic);

Shape (pyramidal, stellate)

Bipolarcells

axon

dendrites

terminalbouton

Variety of Multipolar NeuronsDiffer in terms of:

• genes expressed• chemicals • shape• arborization • connectivity patterns…

Structure function

104 connections per neuron

1014 total interconnections(one hundred trillion)

Dendritic Spines

Myelination

• Insulates axon• Speeds up conduction

without increasing diameter of axon

• Saves energy

Nodes of Ranvier

Neuroglial Cells

• Physical and metabolic support• 90% of cells in brain• Four types

– Astrocytes (maintenance/support)– Oligodendrocytes (myelin)– Ependymal (line ventricles)– Microglia (macrophages)

Einstein’s Brain

Greater number ofneuroglia

Larger inferior parietalcortex