Cognitive Neuroscience Exam 2 study Guide:

What is Cytoarchitectonics?

End of Chapter 2: Categorization of Brain Areas  

∙ Gross Anatomy: Brain organization by Sulci and Gyri,  

∙ Cytoarchitectonics: organizes the brain based on its cellular organization  (based on cortical layers of the brain)  

o Brodmann Regions (52) areas: Cells in different parts of the brain  look different  

 ***If cell look different then they might do something different   ***Structure Determines Function

∙ Functional: When stimulated, different areas of the brain affect areas of the  body differently and vice versa (motor, somatosensory, visual, Auditory,  Olfactory)

o Different neurons fire when these senses are stimulated  

  Sensory cortex: Incoming Info

∙ Primary (1st) more raw info

∙ Secondary (2nd) processes more complicated info

  Motor Cortex: Outgoing info

∙ Primary: The last place info is sent before going to body

What is Wada Test?

∙ Secondary: Before primary processing (initial planning of We also discuss several other topics like language and linguistics notes

motion)

**These systems work in opposite directions**

∙ Know their locations: PMC: pre central gyrus PSSC: post central  gyrus (homunculus)

  Association Cortex 

∙    Most of the Frontal Lobe: Executive functioning , attention,

decision making

∙    Is the last area to mature in the brain  

Hemispheric Lateralization

∙ Contra lateralization: information from one side is processed and received  by the opposite side  

o Somatosensation: cut on left hand, right hemisphere will process it  o Motor cortex: movement on the right side of the body is controlled by the left side  

∙ ***Not all pathways cross over immediately as these ones do o Vision 

 The eyes have overlapping visual fields: both eyes see parts of  both visual fields  

 They are not entirely contra lateral:  

What are the 4 types of mechanoreceptors?

∙ Depending on which visual field information is in, it will  

either cross over to the other side’s Visual Cortex or  

remain on the same side  

∙ Everything in RVF goes to Left Visual Cortex and  

vice versa

∙ Wada Test: Inject anesthetic into one hemisphere stopping the neurons from firing there We also discuss several other topics like what is the term for the voluntary exchange of goods and services between two or more parties?

o Left side asleep:

  Language center not working (LEFT HEMISPHERE) 

 Handed patient a spoon and asked what it was-- Response:  

“Nothing”

∙ Patient is unable to say/remember the object  

 Right side could still get the left hand to point out the spoon  (remembers info but not linguistically)

o Right side asleep:

 Wil not notice too many differences  

o Language areas in the Left Hemispheres  If you want to learn more check out callatians definition

 Broca’s,( Frontal Lobe) Wernicke’s (Temporal Lobe)

 ∙     No visible gross anatomical differences between hemispheres  o Sylvian fissure differences, Planum temporale (language functioning)  ∙     Micro-anatomical differences in the Homotopic regions 

o Homotopic Regions: corresponding regions on each side of the brain  that do not necessarily have the same functions (language area in the  left, same are in the right that does not control language) 

 Cell bodies are bigger in left  

 differences between cells (left vs. right) (subtle)

o Corpus Callosum: largest commissure (white matter fiber that  connects the two hemispheres)

 All functions that deal with COGNITION (which is why we care  about it)  

 Parts:

∙     Genu: front

∙     Body: middle

∙     Splenium: back

o Because of Diffusion Tensor imaging we are able to  

see that white matter connections in the CC are  

ORGANIZED  

o Homotopic vs. Heterotopic Connections 

 Homo: corpus callosum, connects one area of hemisphere with  the corresponding area in the opposite hemisphere  

∙     A A

 Hetero: Connects an area of one hemisphere to a different area  in the opposite hemisphere  

o Theories about how the hemispheres work together;

 Not cooperation more competition (both sides work to solve a  problem but the stronger side will win) If you want to learn more check out eng 222 jmu

Split Brain  

∙ Can only tell through specific testing that a person even is split Brain  (severed corpus callosum)

o Two words in different visual field test  

 Word on left/Word on Right  what will be the response?

  This experiment demonstrates that that the left hemisphere is  better at language and the Right is better at spatial  

understanding  

 Redundant mental lexicons: both hemispheres must be able  to understand the same words, just have different ways of  

expressing knowledge  

∙ What does a Split Brain patient SAY?

o Not conscious of anything but the left side(the interpreter) o Anything the Right hemisphere does that opposes the Left hemisphere  can cause confabulation 

 Not lying, just a (incorrect) justification for why the left hand  (right hemisphere) did something that the left brain was not  

consciously aware of  

∙ EX from class (Left snow/right/chicken foot): “my left hand pointed at the shovel because … I need it to clean up  We also discuss several other topics like anth 307 class notes

after the chickens!”  

o Causal perception (right hemisphere) – info from situation you  actually witnessed  

o Causal inference (left hemisphere)—info from situation you did not  witness but can infer about  

 CI enables us to solve problems  

o Matching Behavior (Left H.) – try to match probabilities of a situation  o Maximizing behavior with random events (Right H.)—just go with  whatever behavior has the best probability (This one works best ,but  we don’t do it as often)

 Holism/Global: Right  

 Feature/Localized: Left 

∙ Partial Corpus Colostomy: cuts part of corpus callosum but not all  o When presented with a word in the Left visual field they will have a  long round about response using descriptions and stories to try to find  the word  

 In a total split brain they would just say “nothing”

o Therefore: right H. cannot speak but it can generate abstract  knowledge that it shares with the left H.  Don't forget about the age old question of metals have low ionization energies and readily share their

∙ Visuospatial tasks:  

o Pattern block test  

o Alien Hand syndrome: competition between the hemispheres (hands) o Right brain (left hand seems to be better)

∙ Face recognition

o Right : more holistic, better at recognizing familiar faces  

o Left: more feature based, better at recognizing self  

∙ Hierarchical Representations:

o Holistic vs. Feature based processing  

 Seeing the forest or the trees?

o Left: Feature based  

 Will see the tiny components that make something up rather  than the whole

o Right : Holistic

 Will see the overall picture better than the tiny parts that make  it up  

∙ Remember: there is no absolute distinction between the hemispheres ∙ Unless you have a severed CC it is hard to see the differences between the  hemispheres because they are always communicating  

∙ Left: the interpreter/consciousness, language  

∙ Right: spatial tasks  

Sensory and Perception

∙ The difference:  

o Sensory: process through which the senses pick up stimuli and  transmit it to the Brain  

o Perception: Process by Which sensory info is actively organized and  interpreted by the Brain  

 Transduction: Process of turning to physical stimulus into  

electrochemical signal (language of neurons)

∙ Light stim—to chemical signals  

 Sensory Adaptation: we are better at detecting changes than  Constant information (stop smelling a smell after a while)

o Audition

 Physical stim.—compression of air molecules into sound waves  (frequencies)

 Amplitude, frequency, Complexity/Timbre

o The ear  

 Auditory Pathway : Vibrations travel through the ear

∙ Outer ear

o Pinna :funnel

o Tympanic membrane: ear drum/ what separates  

outer and middle ear  

∙ Middle ear  

o Malleus, stapes, incus (smallest bones in body)

∙ Inner ear  

o Cochlea (looks like a snail)  

o Basilar membrane: inside of cochlea  

 Stero-cillia (hair cells) 

∙ Process of transduction

∙ Mechano-gated ion channels (protein strip) that opens

or closes bases on which way the hair cell is leaning  

o Slack: closed  

o Taught: open – action potentials  

o The Vestibular sense: balance, orientation of head and body in  space  

 Semicircular canals: hold fluid and can sense when you are  

moving  

o Cochlea:  

 Vibrations in the Stapes pass through a window to the cochlea   The basilar membrane is not consistent throughout the cochlea

∙ Place coding: Depending on where hair cells are on the  basilar membrane (stiff part at the beginning, or more  

loose part at the apex) the Brain knows the frequency of  

a sound depending on where the info comes from  

o Preferential frequency

o Higher frequencies are heard at beginning of  

basilar membrane and lower further into the apex  

 Inner hair cells: turn vibrations into Action Potentials  

 Outer hair cells: receive action potentials that make them  vibrate  

∙ Vibration amplitude system  

∙ Receptive Fields  

o Refers to frequencies not space  

o Brain relies on overlapping neurons to understand frequencies  ∙ Flow of Info to the Brain  

o Superior olivary nucleus inf. Colliculus Medial Geniculate nucleus Primary auditory cortex (Heschl’s gyrus)

 What do these areas do?

o Tonotopic: PAC is organized based on receptive fields of frequencies  o Secondary Auditory cortex: more complex info being processed  o Brain Stem: Sound processing  

 What is the source of the sound?

∙ Vertical Axis question: Dorsal cochlear nucleus  

∙ Horizontal Axis question: Interaural timing and intensity  

(superior olivary nucleus)

 Coincidence Detectors

∙ requires sound to be heard at the same time in order to  

be activated  

∙ What happens when a sound is to the Right or left of us  

o Which ear hears it first and what is the effect of  

this?

∙ Olfaction: Smell  

o Odorants: Chemicals  

 Shape theory: odorants attach to odor receptors  

∙ A single odorant can bind to more than one receptor  

 Vibration Theory

∙ Some receptors have the same shape but are perceived  

as different smells because they vibrate differently  

o Olfactory Pathway  

 Bipolar neuron: olfactory receptor  

∙ Signals sent to the Olfactory Bulb

o Glomeruli: neurons in the OB, receive info from all  

kinds of receptors and figure out the pattern

o Info does not go to thalamus it goes through the  

limbic system  

 Pyriform, Primary Olfactory, secondary  

Olfactory (orbital frontal)

 THIS is abnormal  

∙ Gustation: taste  

o Stimuli: chemical senses  

o Papillae contain Tastebuds  

o Five basic tastes: sweet, sour, salty, bitter, Umami

 Combination of receptors all over the tongue sense these   Know the evolutionary reason we taste  

o Flavor: combination of Smell and Taste 

 Smells can enter nasal cavity through the mouth  

o Pathway

 Straight to Brainstem through the cranial nerves--- thalamus---  Then the Primary Gustatory Cortex  

∙ Somato sensation: body senses

 o Touch, temperature, nociception ,proprioception 

 Proprioception: knowing the location of body parts in Space   Touch : stimulus: pressure  

 Mechano receptors 

∙ Shallow: rapid adapting, more sensitive (reading braille)

∙ Deep: Slow adapting, general info (weight)

o Free nerve endings: pain  

∙ A variety of receptors creates a bigger receptive picture  

 Lateral Inhibition  

∙ Multiple neurons are affected by a stimulus, in order to  

create a more specific message of where you are feeling  

something, the neurons will not only send out an  

excitatory signal BUT it will also send out inhibitory  

signals to neurons next to it to stop them from sending  

signals  

∙ MOST activated neuron will “win”

∙ This gives us Acuity and focus  

 Somato sensory pathways  

∙ Contralateral  

o Touch receptor—spinal cord—medulla—Midbrain—

Thalamus—Primary SS cortex

o Secondary SS cortex: where hemispheric sharing 

happens 

 Specific and sophisticated processing  

∙ Vision

o Physical receptors: light particles/waves

o Parts of the eye (know where they are and what they do)

 Cornea  

 Pupil

 Iris  

 Lens  

 Retina  

∙ Ganglion layer

∙ middle layer(bipolar cells),

∙ Receptor cells  

o Where light is transduced  

 Rods : acuity – seeing in the dark—

peripheral  

 Cones: Color – centrally located on the  

Fovea  

o How is light transduced  

 Photoreceptors contain pigment which  

changes chemically when light hits it

 They release NT and cause AP to go off  

o Blind Spot: where optic nerve connects to retina  

 Light here cannot be transduced but we do not feel as if we have a blind spot

∙ Forward facing eyes/overlapping visual fields/ eye  

movement  

∙ Our brain tends to fill in the gaps through memory,  

expectation

o Fovea: center of Retina, where most cones are,  

 Many more receptors on the Fovea: more detail, acuity   Based on this we should not be able to see color if we are not  looking directly at something, yet we can --- brain fills this in  o Ganglion Cells: carry info out of eye through optic nerve   Ganglion Receptive Field 

∙ Light needs to be projected to a certain space in order for the receptive field to be triggered  

 Center Surround (LGN and Ganglion cells)

∙ Light falling in the Center: excitatory  

∙ Light Falling in the surrounding area: inhibitory  o Similar to lateral inhibition  

∙ This is system makes it easier for us to detect  

borders and edges