B+B e2

Microcircuits ➜ Macrocircuits

Micro. =cells/neurons connected via axons Macro. =(sub)regions/areas connected by tracts/fasciculi

Egocentric (processing)

Relative to you

cognitive processing includes

Sub-personal level

Allocentric (processing)

Two objects relative to each other not including yourself

topology

how networks are connected to each other

degeneracy

many regions : 1 function

critiscisms of connectome theory

-if you are your connectome, you can copy your mapping into anything (AI); immortality -too simple of an answer for us -the brain functions as a result of the dynamic interactions among many dif systems at dif levels of organization -3 extraconnectomic contributions to brain functions: ➜volume transmission ➜neuron glial interactions ➜embodiment

Karl Lashley (19th-20th cen.)

-interested in loco. of memory -lesion based research on rats to see how mem. is affected by dif lesiona at dif parts of brain ↳ No strong relationship bw WHERE he cut + ability ↳ Strong relationship bw HOW MUCH he cut + ability -Led to: EQUIPOTENTIALITY = MANY : MANY mapping

three important topics pertaining to micronetwork motifs

1)Feedforward Excitation/Inhibition 2)Convergence/Divergence 3)Recurrent Excitation (feedback)

tetanus

=rapid firing of action potentials; artificial -if you alter the tetanus, the post-synaptic responds in a different way than before to pre-synaptic neuron -can cause neurons to gain additional receptor(s) to account for more travel - ↑ in action potentials in the pre-syn neurons allows for connection strength plasticity; long-term changes in how post-syn neurons recieves signals from pre-syn neuron

Connectome (from doc)

A map of the neural circuits and connections that make up the entire brain.

Networks of cognition

Biggest message: Behavior is not the result of local function, but rather network function Submessages: Activity in the brain is parallel/distributed Activity: recurrent/recursive pattern of activity

Behavior

the internally coordinated responses (actions or inactions) of whole living organisms (Individuals or groups) to internal and/or external stimuli, excluding responses more easily understood as developmental changes and including cognition at the organismal level- cognitive processing

Macrocircuits

Consists of multiple imbedded microcircuits which together mediate higher brain functions.

Common circuit motifs that mediate the spinal stretch reflex include all of the following EXCEPT: A. Feedforward excitation B. Feedforward inhibition C. Feedback inhibition D. Lateral Inhibition E. Divergence

D. Lateral Inhibition

Topology

How neurons are connected to each other (like topography)

Patient Tan

Issues in language production Studied by Broca, led to the naming of broca's area

Phrenology (18th cen)

-1st attempt to connect structure to function/beginning of functional-specialization view -HOW? ➝ by feeling surface of head for bumps, grooves, size, etc. ↳ "Bump here-you have lots of anger." ↳ "Bump here-you're good at peotry." ↳ "Two bumps there-you're anxious."

Network Function vs Local Function

-BIG MESSAGE: behavior is not the result of LOCAL function, but rather NETWORK function Network Function: -communication across regions of brain -macrocircuits Local Function: -focuses on one specific regions -microcircuits

IMPORTANT ASPECTS OF BEHAVIOR

-Big message: behavior is not the result of LOCAL function, but rather NETWORK function -there is not one single behavior that is a localized function; even speaking is not just located in Broca's area; other regions connected via tracts -Behavior= emergent/collective property; not just local -local functions have roles, but are NOT strong enough individually to produce behavior at the organismal level- need interactions

plausibility of connectome theory

-Connectomes change over time (neurons can gain/ lose branches)(synapses can be created and eliminated)(synapses can grow and shrink) -Evidence that neural activity is encoding our thoughts, feelings, and perceptions -Evidence that neural activity can change your connections-so, experiences can change connectome -Connectome is where nature meets nurture -Neural activity is constantly changing and the connections of the brains neural network determines the pathways along which neural activity flows --Neural activity is the physical bases of thoughts, feelings, and perceptions (theory) --Stream metaphor -Theory of how to possibly read a memory from a connectome --Analyze chain of sequence of neurons/neural activity --See mental disorders in miswiring of connectomes

Paul Broca (19th century)

-Found that injuries to a particular region in the brain resulted in deficits of speech production. -Patient Tan; lesion in L infer. frontal gyrus (Broca's areas) -modularity= modules in the brain for particular abilities -1:1 mapping -HUGE proponent for localization> func. at organismal level due to parts of the brain

Kate + Hemispherectomy

-behavior relatively normal: visual perception issues + limp/no function in right arm -Has: right hemisphere and only medial surface of occipital pole in left hemisphere - 4 most important pts: (plasticity at macro level) 1) function can be REGAINED ↳ lateralization of function 2) EQUIPOTENTIALITY (equal ability) ↳ function is not necessarily localized ↳ combo of Neural Reuse & Pluripotentiality ↳ brain regain can do anything, but has some limits ↳ plasticity is more likely to occur/be successful at a younger age (like Kate) since the functions have not been fully developed yet 3) some limits 4) order of loss of function related to which those functions are developed

volume transmission

-cells that are NOT synaptically connected can still communicate w/ each other -some nts are gases, which diffuse through brain regions that are not synaptically connected (gas ex.: NO) -diffusion barriers -role in learning and creating connections to brain

neuron glial interactions

-connectome ignores important role of glia on consciousness -"the other brain" -crucial interaction not captured by connectomes

embodiment

-organismal level, talks about the role of the body in cognition -body playing a role in cognition: ➜trivial: ears for listening ➜nontrivial: gesturing helps person think -refers to the fact that the body is very involved in our ability to think/cognize -human cognition is a human brain-body-environment function

How is Feedback/Recurrent Excitation implicated in memory?/What does it mean to change synaptic strength?

-to change the connection b/w the pre- & post-synaptic neurons Involvement in memory -pattern of connections/activations is NOT enough to represent memory➜connections: synaptic strength must change!➜(to explain memory) Hebbinian Learning Rule. ★Hebbinian Learning Rule= neurons that fire together, wire together! ★strength increases w/ simultaneous firing -causes changes in response to input -memory is reactivation of this pattern that has been created -learning is change in synaptic connections/is plasticity

long-term potentiation (LTP)

-underlies the permanent change in connections bw neurons -post-tetanic potentiation (PTP)

disorder

1 fairly specific issue/defict ↳ 1 region: 1 deficit= func. specialization view

Smaller submessages about behavior

1) Activity in the brain is parallel and distributed. ➜Parallel: activity occurring at the same time/in sync ➜Distributed: interactions/network function; distributed among many brain regions ➜NOT hierarchical/serial: how people think of brain activity, BUT has been argued/disproved 2) Patterns of activity in the brain are recurrent/recursive (connections between regions). ➜ Pattern of activity motifs seen at micro level can be seen at macro level. ➜ Feedback motifs= loop is recurrent ➜ Feedforward motifs= serially and linearly ➜ parallel: convergence, divergence ➜ motifs are idealized; more realistically, feedback motifs are present

Region Types of Blindness

1) Dorsal stream 2) Ventral stream

Types of Vision

1) High level 2) Low level

Types of Blindness

1) Retinal Blindness 2) Subcortical Blindness 3) Cortical Blindness

key points on visual perception

1) Visual system= somewhat hierarchically organized 2) Beyond occipital cortex: ↳ Dorsal visual system (goes to Parietal lobe) ↳ Ventral visual system (goes to Temporal lobe) 3) High-level (Late) vision & Low-level (early) vision: ↳ Low-level/Early= orientation, motion, color, line-length, texture ↳ High-level/Late= whole objects, faces, relative space, visual imagery, predicting

3 extraconnectomic contributions to brain functions/levels of organization:

1) volume transmission 2) neuron glial interactions 3) embodiment

structure-function relationships

2 Main Views: 1) Functional specialization/specificity 2) Neural reuse/pluripotentiality ↳ don't have specialized functions; can be used + reused in dif. contexts -both views subscribe to network view Main Ideas From Discussion: ↳ Behavior= NOT the result of local function, but of NETWORK FUNCTION ↳ Behavior= an EMERGENT property ↳ Brain activity= PARALLEL during behavior + is DISTRIBUTED

Connectome

= a complex map showing all the neural connections in the brain -only have been able to map out the connector of C. elegans -node=neuron -line=connection -our connectome contains 1 million x more connection than our genome has letters

Connectome theory presented in vid.

= memories ar stored in the connection b/w our brain's neurons (may also be true for personality) -dont have enough tech to construct a human brain's connectome -neurons connect to so many other neurons b/c of their points of contact-synapses

Hebbian learning rule

=2 neurons fire at the same time, synapse will increase; "neurons that fire together wire together!" =a synapse will change its strength if that synapse is active (i.e., releases transmitter) and, at the same time, the postsynaptic cell is active. ★strength increases w/ simultaneous firing -causes changes in response to input -memory is reactivation of this pattern that has been created -learning is change in synaptic connections/is plasticity

Plasticity

=ability of neurons and/or regions to alter their connections following injury, learning/memory =(re)gaining ability; changes in where local functions happen ➜ can gain ability to learn a new language or memorize something ➜ can Regain an ability lost to damage ---ex: damage to entire Broca's area, but ability to speak is regained since other regions gained this function ➜ changes at both the macro and micro levels ➜ reconfigure/redirect connections bw local regions ➜ refer back to river/riverbed metaphor for plasticity

Feedback/recurrent excitation

=presynaptic neuron excites a postsynaptic neuron, which then loops and excites the presynaptic neuron -In Panel F1, a presynaptic neuron excites a postsynaptic neuron and that postsynaptic neuron excites the presynaptic neuron. This type of circuit can serve a switch-like function because once the presynaptic cell is activated that activation could be perpetuated. Activation of the presynaptic neuron could switch this network on and it could stay on. Panel F2 shows variants of feedback excitation in which a presynaptic neuron excites a postsynaptic neuron that can feedback to excite itself (a, an autapse) or other neurons which ultimately feedback (b) to itself.

Microcircuits

A few interconnected neurons that can perform sophisticated tasks such as mediate reflexes, process sensory data, generate locomotion, and mediate memory/learning.

Feedforward inhibition

A presynaptic cell excites an inhibitory interneuron (an interneuron is a neuron interposed between two neurons) and that inhibitory interneuron then inhibits the next follower cell. This is a way of shutting down or limiting excitation in a downstream neuron in a neural circuit. Stops message. Pre- hyperpolarizes (away from threshold) the post-syn. neuron.

Lateral inhibition

A presynaptic cell excites inhibitory interneurons and they inhibit neighboring cells in the network. This type of circuit can be used in sensory systems to provide edge enhancement.

Research Methodologies

A systematic way to look a hypothesis In neuroscience common methods are split into two major groups, causal and correlational Causal Direct Cortical Stimulation Electric current applied directly to cortex (the brain is exposed) Transcranial Direct Current Stimulation (TDCS) Electric current directly to the cortex through the cranium (the brain is not exposed) Transcranial Magnetic Stimulation (tMS) Temporarily knocks out a region; loss of function; "virtual stroke" Lesion Method Take a part of a brain out and see what function(s) have been lost (non-humans); wait for a human to have a stroke, head trauma, etc., and see what function(s) are lost.

Feedforward inhibition

Action potential in the presynaptic neuron causes postsynaptic to be less likely to fire

Feedforward excitation

Action potential in the presynaptic neuron makes postsynaptic neuron more likely to fire

Convergence

Allows a neuron to receive input from many neurons in a network. When the muscle is stretched, not one, but multiple sensory neuron are activated and these sensory neurons all project into the spinal cord where they converge on to individual extensor motor neurons. So, the stretch reflex is due to the combined effects of the activation of multiple sensory neurons and extensor motor neurons.

Divergence

Allows one neuron to communicate with many other neurons in a network. A single sensory has multiple branches that diverge and make synaptic connections with many individual motor neurons. Therefore, when the muscle contracts as a result of the neurologist's tapper, it does so because multiple muscle fibers are activated simultaneously by multiple motor neurons.

Feedforward excitation

Allows one neuron to relay information to its neighbor. Long chains of these can be used to propagate information through the nervous system. Continues message. Pre depolarizes post (leads to AP)

Action Potential

An electrical signal that travels within neurons and allows for communication between neurons by causing the release of neurotransmitters.

Lesion-Deficit Analysis

An old method of investigation in systems neuroscience in which scientists take away a specific section of an animal's brain (or a human's, if one is deeply unethical) and watch what happens.

The process by which a neuron summates synaptic excitation and inhibition is called: A. Plasticity B. Integration C. Convergence D. Pulse frequency modulation E. Disinhibition

B. Integration

Behavioral Definition for this course

Behaviors are caused by an internal/external stimuli

The network motif that underlies circadian rhythms is: A. Temporal summation B. Spatial summation C. Feedback inhibition D. Feedback excitation E. Lateral inhibition

C. Feedback inhibition

Feedforward excitation ex.

Feedforward excitation circuit that mediates a behavior: the branch to the left that forms a synaptic connection (green triangle) with an Extensor (E) motor neuron (colored blue). The action potential in the sensory neuron invades the synaptic terminal of the sensory neuron causing the release of transmitter and subsequent excitation of the motor neuron. The stretch to the muscle leads to an action potential in the motor neuron (MN), which then propagates out the peripheral nerve to invade the synapse at the muscle, causing the release of transmitter and an action potential in the muscle. The action potential in the muscle cell leads to a contraction of the muscle and an extension of the limb.

Dorsal vs. Ventral Streams

First type: Dorsal is the where ( as in an object relative to you) and Ventral is the what (as in what is something) Second type: Dorsal is the how (to do) something is and the ventral is again the what is something. Third type: Dorsal is egocentric (where is something relative to me), ventral is allocentric (where are things relative to each other) Egocentric/Allocentric refer to whether something is perceptual or an action. Ex: If a piece of paper is 5 feet from a pencil, and the task is to move the pencil an equal distance away (so 10 feet), To move the object would be an allocentric action task. If my hand was 5 feet away from the paper, and I had to move my hand to touch the paper, it would be an egocentric action task. Ex. Determining the distance between the paper and the pencil would be an allocentric perceptual task Perceptual/Action depends on the context given

Functional Specificity

Function is localized to specific parts/regions of the brain Local regions are specified for one function

Functional Specialization VS Neural Reuse

Functional Specialization: ↳ fMRI single structures: focus on 1 ability to see what region is activated Neural Reuse: ↳ fMRI meta-analysis: cross studies; finds evidence that regions are evolved in many things/gets activated in dif. tasks ↳ Relate to degeneracy: degeneracy= multiple regions support 1 function

Neural Circuits

Groups of neurons connected by synapses that carry out a certain function when activated through action potentials. Three Types: Nanocircuits: Networks within individual neurons that make up the biochemical machinery required for mediating key neuronal properties. Microcircuits: A few interconnected neurons that can perform sophisticated tasks such as mediate reflexes, process sensory data, generate locomotion, and mediate memory/learning. Macrocircuits: Consists of multiple imbedded microcircuits which together mediate higher brain functions.

Feedback/recurrent inhibition

In Panel E1, a presynaptic cell connects to a postsynaptic cell, and the postsynaptic cell in turn connects to an interneuron, which then inhibits the presynaptic cell. This circuit can limit excitation in a pathway. Some initial excitation would be shut off after the red interneuron becomes active. In Panel E2, each neuron in the closed chain inhibits the neuron to which it is connected. This circuit would appear to do nothing, but it can lead to the generation of complex patterns of spike activity.

Sub-personal level

Level underneath organismal; how do I go about doing something? Subconsciously. example: orienting fingers in such a way that allows you to grasp a piece of chalk/finger movements involved in picking up chalk and using chalk

inhibitory neuron (IPSP)

Makes it less likely for postsynaptic Neuron to fire. Has to be stimulated by an excitatory neuron so that it can inhibit the signaling of the nest neuron

excitatory neuron (EPSP)

Makes it more likely for postsynaptic neuron to fire

Degeneracy

Many regions supporting one function/different assemblies of structures can perform the same function.

Riverbed Metaphor

Meant to describe plasticity Where the water flows, the riverbed will get bigger as it is worn down It is possible for the water to start flowing along a new path

Microcircuit motif and their relation to Macrocircuits

Micro. Motifs: -feedforward: linear messaging -convergence: many-to-one neuron -divergence: one-to-many neurons -feedback/recurrent: loop; goes to other neurons & also synapses to itself/post-synapses back to pre-synapse Relation to Macro.: macrocircuits also have these same motifs ↑, but instead of focusing on individual neurons, focused on brain regions

Macrocircuits vs connectome (subpersonal levels)

Microcircuits: ➜can itself be consisted of other macrocircuits (which are then composed of microcircuits) ➜regions/subregion connected via tracts/fasciculi ➜smaller scale; subset of connectome ➜trying to describe what ius going on on the behavioral level Connectome: ➜shows just neurons connected via synapses ➜more abstract level ➜outlines ENTIRE thing ➜just itself

Structure function relationships

More generalized than functional specificity Ex. Occipital lobe's function is vision

Nanocircuits

Networks within individual neurons that make up the biochemical machinery required for mediating key neuronal properties.

Divergence

One neuron can make a divergent connections to many different postsynaptic neurons (One → many)

Convergence

One postsynaptic cell receives convergent input from a multitude of different presynaptic cells (Many → one)

Convergence/Divergence

One postsynaptic cell receives convergent input from a number of different presynaptic cells and any individual neuron can make divergent connections to many different postsynaptic cells. Divergence allows one neuron to communicate with many other neurons in a network. Convergence allows a neuron to receive input from many neurons in a network.

action potential

Sets everything in motion; "all or nothing;" once you hit threshold, AP happens - can get more action potentials, but will be same size

Neural Reuse

The idea that function is not confined solely to specified sections of the brain, and that in the case of significant circumstances (eg: damage/lesions) different sections of the brain can take over/reroute brain function.

Computational Metaphor for the Brain

The idea that the brain functions as a biological computer device through symbolic processing. (Connected strongly with the ideas of Cognitivism and Computationalism.)

synaptic depression

What?: = An AP in the sensory neuron produces an EPSP in the motor neuron. A 2nd AP in the sensory neuron, 200 msecs after the 1st, produces an EPSP that is SMALLER than that produced by the 1st AP Why?: Depletion of available transmitter; 2nd AP will RELEASE LESS transmitter bc LESS transmitter is AVAILABLE to be released.

Synaptic facilitation

What?: = 2 APs in the presynaptic cell produce 2 EPSPs in the postsynaptic cell. 1st AP produces a 1 mV EPSP, 2nd AP (occurring ~ 20 msecs after the 1st) produces an EPSP LARGER than the EPSP produced by the 1st AP; 2nd 2X as large as 1st. ➝ MORE AP in SHORTER time= MORE intense response Why?: Residual calcium ↳ AP leads to opening of Ca2+ channels + influx of Ca2+, which leads to release of transmitter ↳ After 1st AP: Ca2+ levels DECREASE back to initial level, BUT recovery= NOT instant ➝ if 2nd AP is initiated before calcium recovers to basal level, Ca2+ influx of 2nd spike will ADD to the "Residual Calcium" left over from the first

Ethogram

a catalog or table of all the different kinds of behavior or activity observed in an animal.

Syndrome

a collection of problems ↳ Broca: a syndrome= damage in multiple regions ↳ Lashley: damage in one area can cause probs bc 1 area supports many functions

Recurrent excitation

a presynaptic neuron excites a postsynaptic neuron and that postsynaptic neuron excites the presynaptic neuron (learning loop)

Diffusion Tensor Imaging (DTI)

a technique used to produce images of the brain that shows connections among different regions -showing diffusion along tracts in brain

systems neuroscience

behavior is supported by interacting components; typically studied at macro scale; macro systems are composed of micro systems

Neuron-glia interaction

connectome ignores important role of glia on conciousness

genome

entire sequence of DNA

Correlational

fMRI Measures oxygenations leves in regions of the brain, level of oxygen cocrelates with the amount of engery/activty that the specific region is using. Diffusion Time Imagery (DII) Uses fMRI technology to show structural connections. Electroencephalogram (EEG) High temporal resolution and low spatial resolution We know when changes in brain activity are happening, but not where they are happening

Interneuron

interposed between one neuron (here the SN) and another neuron (here the MN).

motif

kinds of connections in a certain circuit (set of neurons)/what those connections are

nanocircuits

networks within neurons; underlying biochemical machinery for mediating key neuronal properties such as learning and memory and the genesis of neuronal rhythmicity

intrinsic plasticity

(homosynaptic mechanisms) -refer to changes in strength of synapse that are brought about by its own activity; changes happens WITHIN the synapse - 2 types: 1) synaptic depression 2) synaptic facilitation

Neural Reuse/Pluripotentiality

- 1:MANY mapping; 1 region can support many functions - M1 (primary motor cortex) & V1 (primary visual) ↳precentral gyrus ↳occipital lobe ➝ while they are essential for movement + sight, they are also used when thinking about movement + thinking about visual stimuli

functional specialization

- functions= LOCALIZED - local regions: specialized for ONE function - allows for recovery of function, BUT there are some issues w/ explaining recovery (if area A takes up function of area B, then area A's og function is gone; DONT see this) - 1:1 mapping - new abilities gained over time in newly specialized area ↳ ex.: written language established >1000 yrs ago; need new area for it (VWFA) ↳ FFΔ, PPΔ, EBO, VWFA; where functions occur is typically stable, but could differ due to trauma

synaptic plasticity

plasticity at the micro level

Feedforward inhibition ex.

right branch of the axon of the sensory neuron shown. The action potential in the sensory neuron invades the synaptic terminal of the sensory neuron causing the release of transmitter, and subsequent excitation of the postsynaptic interneuron colored black. The excitation of the interneuron leads to the initiation of an action and the subsequent release of transmitter from the presynaptic terminal of the interneuron (black triangle), but for this branch of the circuit, the transmitter leads to an IPSP in the postsynaptic flexor (F) motor neuron (colored red). The functional consequences of this feedforward inhibition it is to decrease the probability of the flexor motor neuron becoming active and producing an inappropriate flexion of the leg.

organismal level

thinking, behavior of whole organism; can think of cognition at level of whole organism example: picking up chalk and using it to write