How we know what we know Macrostructure of the brain

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How we know what we know Macrostructure of the
brain

• Brain Language
• LING 411/412/489
• NSCI 411/611/489
• Harry Howard
• Tulane University

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Course administration

• Pass around roster
• Are the 3 students who didn't show up on
  Wednesday here?
• I asked the Help Desk about Jennifer Nikhil
• Nikhil is currently enrolled in this course.
  Jennifer doesn't presently have a BB profile, but
  if she registered after Aug 29th, her profile
  won't be on the system yet as all data feed from
  the registrar were shut down for the hurricane.
  The next data feed will run tonight at 7 pm, at
  which time Jennifer's profile will be created if
  she has indeed registered for courses.
• http//www.tulane.edu/ling/LING411/
• Readings are found BB BrainLanguage_CC Brain
  and Language(Combined) Course Documents
• Service Learning was supposed to sent a rep
  today I don't know

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How we know what we know

• Methodology

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Osterhout et al. 2006 1, 2

• What are the primary methods of investigation and
  how do they work (in a very general sense)?
• What are the advantages and disadvantages of each?

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Phrenology
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Short history of research
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Overview of methodologies

• Lesions
• Wada test
• Craniotomy cortical stimulation
• Corpus callosotomy split-brain patients
• Hemifield tachistoscopy
• Dichotic listening
• Imaging C(A)T, PET, (f)MRI
• Electromagnetic EEG, MEG - not today
• Transcranial magnetic stimulation (TMS)

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Lesions

• A lesion is a non-specific term referring to
  abnormal tissue in the body. It can be caused by
  any disease process including trauma (physical,
  chemical, electrical), infection, neoplasm,
  metabolic and autoimmune.

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Wada test

• The Wada test (named for a neurologist, Juhn A.
  Wada) consists of behavioral testing after the
  injection of an anesthetic (such as sodium
  amobarbital or sodium methohexital) into the
  right or left internal carotid artery.
• Depending on how the injection is made (and the
  quantity), there is a certain amount of time
  during which the activities of one of the
  cerebral hemispheres are suspended, so the
  abilities subserved by the other hemisphere can
  be tested in isolation.

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Craniotomy cortical stimulation

• A craniotomy is a surgical operation in which
  part of the skull, called a skull flap, is
  removed in order to access the brain.
• Craniotomies are necessary for many types of
  surgery they are also widely used in
  neuroscience in techniques such as extracellular
  recording, brain imaging, and manipulations such
  as electrical stimulation and chemical titration.
• Human craniotomy is usually performed under
  general anesthesia but can be also done with the
  patient awake using a local anaesthetic and
  generally does not involve significant discomfort
  for the patient.

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Corpus callosotomy (split-brain patients)

• Split-brain is a lay term to describe the
  result of severing the corpus callosum to some
  degree.
• The surgical operation to produce this condition
  is called corpus callosotomy.
• It is rarely performed, usually only in the case
  of epilepsy, in order to mitigate the risk of
  accidental physical injury by reducing the
  severity and violence of epileptic seizures.

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Corpus callosotomy (split-brain patients), cont.

• A patient with a split brain, when shown an image
  in his or her left visual field (the left half of
  what each eye sees), will be unable to name what
  he or she has seen.
• This is because the speech control center is in
  the left side of the brain in most people and the
  image from the left visual field is sent only to
  the right side of the brain.
• Since the two sides of the brain cannot
  communicate, the patient can't name what he or
  she is seeing.
• The person can, however, pick up a corresponding
  object with their left hand, since that hand is
  controlled by the right side of their brain.

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Divided visual-field (hemifield) tachistoscopy

• A tachistoscope is a device that displays
  (usually by projecting) an image for a specific
  amount of time. It can be used to increase
  recognition speed, to show something too fast to
  be consciously recognized, or to test which
  elements of an image are memorable. Actual
  tachistoscopes use a slide or transparency
  projector equipped with the mechanical shutter
  system typical of a camera. The slide is loaded,
  the shutter locked open, and focusing and
  alignment are adjusted, then the shutter is
  closed. When ready for the test, a shutter speed
  is selected, and the shutter is tripped normally.

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Divided visual-field (hemifield) tachistoscopy,
cont.

• Before computers became ubiquitous,
  tachistoscopes were used extensively in
  psychological research to present visual stimuli
  for controlled durations. Some experiments
  employed pairs of tachistoscopes so that an
  experimental participant could be given different
  stimulation in each visual field.

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Dichotic listening

• Dichotic Listening is a procedure commonly used
  for investigating selective attention in the
  auditory domain. Two messages are presented to
  both the left and right ears (one message to each
  ear), normally using a set of headphones.
  Normally, participants are asked to pay attention
  to either one, or both (divided attention
  condition) of the messages and may later be asked
  about the content of both.
• It was developed to mimic processing demands in
  the natural world, where sensory overload is
  common. Consider the cocktail party or, more
  appropriate for today, the wine-tasting party. We
  may attempt to speak with one individual, but the
  speaker's voice is intermixed with a multitude of
  incoming auditory signals conversations going on
  about us, music from the compact disc player, the
  clatter of plates being filled at the buffet
  table, the children watching a video in the next
  room. Despite this cacophony of sound, we are
  quite proficient at focusing on the relevant
  signalthe words being spoken by our
  conversational partner.

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Dichotic listening, cont.

• In the seminal study of Kimura (1961a), the
  stimuli were digits, presented so that one digit
  was heard in the left ear at the same time as a
  second digit was heard in the right ear. Kimura
  found that people were much more likely to report
  having heard the stimuli presented to the right
  ear, an effect dubbed the right-ear advantage.
  Kimuras usage of dichotic listening to confirm
  the lateralization of language to the left
  hemisphere in normal subjects was soon
  substantiated by studies with lesioned subjects.
  Kimura (1961b) showed that patients with left
  temporal lobe lesions performed worse at the task
  than did patients with right temporal lobe
  lesions. In addition, split-brain patients showed
  a considerable right ear advantage in a study
  using words as stimuli. They succeeded in
  recognizing words presented to the right ear, but
  performed no better than chance for words
  presented to the left ear, see Milner, Taylor,
  and Sperry (1968) and Sparks and Geschwind (1968).

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Computerized (Axial) Tomography (CT/CAT)

• Computed tomography (CT), originally known as
  computed axial tomography (CAT or CT scan),
  employs tomography (digital geometry processing)
  to generate a 3D image of the internals of an
  object from a large series of two-dimensional
  X-ray images taken around a single axis of
  rotation.

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Positron Emission Tomography (PET)

• To produce a PET scan, a patient is administered
  a solution of a metabolically-active substance,
  such as glucose, tagged with a positron-emitting
  isotope. The substance eventually makes its way
  to the brain and concentrates in areas of high
  metabolism and blood flow, which are presumably
  triggered by increased neural activity. The
  positrons emitted by the isotopes are collected
  by detectors arrayed around the patients body
  and converted into signals which are amplified
  and sent to a computer for construction of an
  image.

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PET vs CT

• PET differs from CT in that it uses the bodys
  basic biochemistry to produce images. The
  positron-emitting isotope is chosen from elements
  that the body already uses, such as carbon,
  nitrogen, oxygen, and fluorine. By relying on
  normal metabolism, PET is able to show a
  biochemical change even in diseases such as
  Alzheimers in which there is no gross structural
  abnormality.

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Magnetic Resonance Imaging (MRI)

• In 1977, a team lead by Raymond Damadian produced
  the first image of the interior of the human body
  with a prototype device using nuclear magnetic
  resonance. Damadians device uses liquid helium
  to supercool magnets in the walls of a
  cylindrical chamber. A subject is introduced into
  the chamber and so exposed to a powerful magnetic
  field. This magnetic field has a particular
  effect on the nuclei of hydrogen atoms in the
  water which all cells contain that forms the
  basis of the imaging technique.

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Magnetic Resonance Imaging (MRI)

• All atoms spin on their axes. Nuclei have a
  positive electronic charge, and any spinning
  charged particle will act as a magnet with north
  and south poles located on the axis of spin. The
  spin-axes of the nuclei in the subject line up
  with the chambers field, with the north poles of
  the nuclei pointing in the southward direction
  of the field. Then a radio pulse is broadcast
  toward the subject. The pulse causes the axes of
  the nuclei to tilt with respect to the chambers
  magnetic field, and as it wears off, the axes
  gradually return to their resting position
  (within the magnetic field). As they do so, each
  nucleus becomes a miniature radio transmitter,
  giving out a characteristic pulse that changes
  over time, depending on the local
  microenvironment surrounding it. For example,
  hydrogen nuclei in fats have a different
  microenvironment than do those in water, and thus
  transmit different pulses. Due to such contrasts,
  different tissues transmit different radio
  signals. These radio transmissions can be
  coordinated by a computer into an image. (Gregg
  2002, based on Horowitz 1995) This method is
  known as magnetic resonance imaging (MRI), and it
  can be used to scan the human body safely and
  accurately

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functional Magnetic Resonance Imaging (fMRI)

• An elaboration of MRI called functional MRI
  (fMRI) has become the dominant technique for the
  study of the functional organization of the human
  brain during cognitive, perceptual, sensory, and
  motor tasks. As Gregg (2002) explains it, the
  principle of fMRI imaging is to take a series of
  images in quick succession and then to analyze
  them statistically for differences. For example,
  in the blood-oxygen-level dependent (BOLD) method
  introduced by Ogawa et al. (1990), the fact that
  hemoglobin and deoxyhemoglobin are magnetically
  different is exploited. Hemoglobin shows up
  better on MRI images than deoxyhemoglobin, which
  is to say that oxygenated blood shows up better
  then blood whose oxygen has been depleted by
  neural metabolism. This has been exploited in the
  following type of procedure a series of baseline
  images are taken of the brain region of interest
  when the subject is at rest. The subject then
  performs a task, and a second series is taken.
  The first set of images is subtracted from the
  second, and the areas that are most visible in
  the resulting image are presumed to have been
  activated by the task.

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Macrostructure

• The parts of the brain that you can see with the
  naked eye

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Questions

• What are the axes of the brain?
• What are the lobes of the brain and what do they
  do?
• What are the main connections between parts of
  the brain?
• What are the three ways of referring to areas of
  the brain?

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Macrostructure overview

• Three axes of the brain
• Vertical
• Horizontal
• Longitudinal
• Lateral
• Connections
• Naming conventions
• Gyrii sulcii
• Brodmanns areas
• Stereotaxic (Talairach) coordinates

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Vertical axis ventral/dorsal

• Orientation of picture
• Which way is forward?
• to the left cerebellum at back
• Which hemisphere do we see?
• medial side of right left is cut away sagittal
  view
• Vertical axis
• Dorsal is up, like dorsal fin (dorsal comes from
  Latin word for back)
• Ventral is down (ventral comes from Latin word
  for belly)
• Cortical vs. subcortical division
• Cerebrum vs. cerebellum
• Cerebral cortex (neocortex) vs. cerebellar cortex

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Longitudinal axis anterior/posterior

• Lobes
• Sylvian fissure
• Perisylvian area

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Longitudinal axis, functions
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Motor somatosensory homunucli (sg. homunculus)
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Lateral axis left/right
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Lateral axis

• General
• Which way is anterior?
• Motor and sensory organs are crossed
• Ipsilateral, contralateral
• LH
• Language
• Math
• Logic
• RH
• Spatial abilities
• Face recognition
• Visual imagery
• Music

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Connections

• Corpus callosum

• Arcuate fasciculus

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Naming conventions

• How to refer to specific areas of the brain

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Gyrii

• AnG - angular gyrus
• FP - frontal pole
• IFG - inferior frontal gyrus
• IOG - inferior occipital gyrus
• ITG - inferior temporal gyrus
• LOG - lateral occipital gyrus
• MFG - middle frontal gyrus
• MTG - middle temporal gyrus
• OG - orbital gyrus
• oper - pars opercularis (IFG)
• orb - pars orbitalis (IFG)
• tri - pars triangularis (IFG)
• poCG - postcentral gyrus
• preCG - precentral gyrus
• SFG - superior frontal gyrus
• SOG - superior occipital gyrus
• SPL - superior parietal lobe
• STG - superior temporal gyrus
• SmG - supramarginal gyrus

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Sulcii

• cs - central sulcus (Rolandic)
• hr - horizontal ramus
• ifs - inferior frontal sulcus
• ios - inferior occipital sulcus
• ips - intraparietal sulcus
• syl - lateral fissure (Sylvian)
• los - lateral occipital sulcus
• ls - lunate sulcus
• pof - parieto-occipital fissure
• pocs - postcentral sulcus
• precs - precentral sulcus
• sfs - superior frontal sulcus
• tos - transoccipital sulcus
• vr - vertical ramus

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Brodmanns areas
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Brodmanns areas, functions
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Stereotaxic (Talairach) coordinates

• MRI scans vary greatly between individuals due
  to differences in slice orientation and brain
  features (i.e. brain size and shape varies
  across individuals). Therefore, it is generally
  useful to normalize scans to a standard
  template. Normalization is the process of
  translating, rotating, scaling, and maybe warping
  a brain to roughly match a standard template
  image. After normalization, it is possible to
  report locations using stereotaxic (Talairach)
  coordinates, which are three numbers (X,Y,Z) that
  describe the distance from the anterior
  commissure (the 'origin' of Talairach space). The
  X,Y,Z dimensions refer to left-right,
  posterior-anterior, and ventral-dorsal
  respectively. So 38x-64x58mm refers to a point in
  right posterior dorsal region of the brain.

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Next class

• Visual cognition
• Norman (200273-96)
• Palmeri Gauthier (2004)

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Questions (already sent)

• The visual system splits into two pathways. Be
  able to explain what each does and give one piece
  of evidence in support of each distinction.
• What is the difference between constructivist and
  ecological approaches to vision?
• What steps does the visual system go through to
  identify an object? You should have a rough idea
  of where the cerebral area is that performs each
  step.