Brain Bee Chapter 4

How was Henry Molaison influential to neuroscience?

He suffered from a severe seizures following a blow to the head. He underwent a surgery 18 years later that removed parts of medial temporal lobe (most of his 2 hippocampi). Siezures stopped but he had amnesia. Couldn’t form new memories but everything else continued regularly. Died at 82 2008 after showing the importance of hippocampi and parahippocampal region.

Medial Temporal lobe

Hippocampus and parahippocampal regions

Works with other regions of cerebral cortex to integrate memory.

How are types of memory are processed differently?

Hippocampus, parahippocampal regions, and parts of cortex work together to produce factual and eventful memories.

Emotional and behavioral memories formed by amygdala, striatum (biggest part of basal ganglia), and cerebellum.

Declarative memory

Memory for facts, events, and data. You can subconsciously recall and describe the info.

Semantic or episiodic

Semantic memory?

Declarative memory

Cultural knowledge, ideas, and concepts accumulated about the world

Definitions, math, etc

Involves cortical regions far beyond the hippocampus

Episodic Memories and the 3 brain structures that encode them

Declarative memories

Unique representations of your personal experiences

Mentally recalling specifics about an experience

amygdala mediates emotional significance tied to memories of experiences/events. Parahippocampal regions aids hippocampus in encoding the “what” rather than the “where” or “when”

Long-term memory

episodic and semantic memories are long-term forms of declarative memories

Stored throughout a broad network of cortical areas

Working memory

Short-term form of declarative memory that lets you hold needed and currently used information in the near future

unlike for long-term memory, the Brian does not have unlimited space for working memory, Disappears after seconds unless transformed into long-term memory.

prefrontal Cortex? PFC

“brains executive” attention, decision-making, and long-term planning

Coordinates some aspects of working memory and long-term memory

PFC is particularly active when keeping something like a phone number in mind

Animals studies show neurons in PFC fire in spurts, keeping info alive in working memory

Dentate gyrus

Portion of hippocampus responsible for memories of events

One of the only places of adult brain where neurogenesis (neurons generated from neural stem cells) takes place

Glia help migrate them to accurate location\Some will mature into different types of crucial neurons

Spatial memory

facet of declatative memory, specific neurons or discrete areas are used for processing specific types of information.

For example when navigating a known room, “place cells” in the hippocampus light up

What have mine shown when navigating a maze?

Mice navigating a maze display specific sequences of neuronal activity devoted to right or left turns

Patterns become more distinct as they learn to navigate maze

Learning complex navigational routes causes changes in hippocampus

“Grid cells”

Located in entorhinal cortex, they represent coordinates that allow the brain to track your position is space when external cues are absent.

Entorhinal cortex

medial temporal lobe, acts as a major network hub and the primary bidirectional gateway between the hippocampus and the neocortex (outermost part of cerebral cortex, works for higher-level thinking)

Nondeclarative memory

Implicit or procedural memory, stored and received without conscious effort. Used when performing learned motor skills

The fact that HM and other people show deficits in some types of memories but not others indicates different types of memories are encoded in operate but interacting regions of the brain.

Synaptic Plasticity

Form memories and rewire itself in response to experiences because circuits in your Brian change at synapses

Ability of synapses to remodel themselves

Encoding new long-term memory involves…?

persistent changes in the number and shape of synapses, as well as the amount of NT released and the amount of receptors on the postsynaptic membrane

what was the sea slug Alysia Californica studied for?

Important animals model for the first few neuroscientists studying neuroplasticity because its nerve cells are few and easy to observe.

identified chemical and structural changes in relevant nerve cells that correlated with simple forms of learning and memory.

genes governing ___ are escpically important in the formation of long-term memories

A type of glutamate receptor - N-methyl-d-aspartate (NMDA)

A molecule called cAMP-response element binding protein (CREB)

What are the two opposing processes key for synaptic plasticity

Long-term potentiation (LTP) and long-term depression (LTD)

Long-term potentiation

Long lasting increase in synaptic strength which occurs in many brain regions but especially in the hippocampus

experience physically changes our brain through LTP, shown in many animals studies to be essential for long-term memory consolidation

long-term depression

Decreases a synapse’s effectiveness

Process of LTP

Varies depending on type of neuron

Involves an increase in the number of glutamate receptors on the post-synaptic neuron. This strengthens a synapse by allowing the entry of more electrically conductive ions

The NMDA and AMPA (a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) classes of glutamate receptors are ion channels. They permit CA and NA ions, respectively, to flow into the cell.

What do calcium ions do?

Function as secondary messengers — signaling neurons that set odd a chain of molecular events within cells.

LTP boosts the concentration of CA ions in a postsynaptic cell while LTD increases it to a lesser degree

Different concentrations of CA activate different enzymes that change the synapse, changing its efficiency at relaying nerve impulses

-Kinase protiens= LTP Phosphates=LTD

Process of LTD

Series of molecular events stabilize the synaptic change: Increase in calcium ions within the post-synaptic cell activates cyclic adenosine monophosphate (cAMP) molecules. This activates many enzymes, some that increase the number of receptors making the synapse more sensitive to NT.

Continued stimulation through repetitive experience activates ___?

CREB

acts in the nucleus of a neuron to switch on a series of genes, many of which direct protein synthesis.

Includes neurotrophins. which stimulate the growth of the synapse and structural elements, stabilizing increased sensitivity to NT

-Essential for memories to become long-term

Where are declarative memories stored?

Encoded in the hippocampus, then transferred to the frontal lobes for long-term storage and consolidation. Over time the hippocampus becomes less important for retrieving older memories, frontal cortex more.

How can new research aid synapse related treatments?

enable artificial manipulation of synaptic plasticity

treatments could be developed for synapse-related neurological disorders, such as eradication of harmful memories tied to PTSD, or for boosting our ability to learn & remember.

What happens to emotional responses after repeated exposure?

Learned emotional responses become attached to stimuli over time after repeated exposure

Emotional memory-part of non-declarative memory

What are the 6 basic emotions, who identified them, and extra

Anger, fear, disgust, joy, sadness, surprise

Anthropologist Paul Ekman 1970’s

Disputed number and attributes of human emotion, whether emotions are consistent, and how to define an emotion

Some neural circuits linked to physiological response that help us survive, set goals, interact, and initiate actions

Oxytocin and its impact with the prairie voles

Brain chemical most closely linked to love

Prairie voles mate for life and when oxytocin receptor levels were increased in the brain, female voles formed partner preferences faster

Brain structures most closely linked to emotion and how they are interconnected

Amygdala, the insulation or insular cortex, and the periaqueductal gray (locate in midbrain)

Nurons from the prefrontal cortex, amygdala, and the insular cortex project to the periaqueductal grey, which in turn has reciprocal connections with the central nucleus of the amygdala and projects to the thalamus, hypothalamus, brainstem, and deep layers of the spinal cord

amygdala

Integrates emotions, emotional behavior, and motivation

It interprets fears, differentiates friends from foe, and identifies social rewards

Classical conditions: A form of learning where a stimulus is associated with a reward or punishment

Insula (insular cortex)

disgust (can protect from eating/inhaling harmful chemicals)

Implicated in feeling and anticipating pain (exact function in this area is not understood)

Believed to take in system-wide inputs and generate subjective feelings about them; thus linking feelings, internal physiological states, social emotions, and conscious actions.

Periaqueductal gray

Located in a region where incoming sensory information is acted on by higher brain centers, has been tied to pain perceptions and stress responses such as defensive and reproduction behaviors, maternal attachment, and anxiety

Receptors for pain-reducing compounds such as morphine and oxycodone are clustered in here

human activities are driven by___?

necessities: Food, sleep, sex, avoidance of pain. AND by rewards

but responses and actions aren’t always logical. Little is known about how brain transforms feelings → decisions

Theoritical models about decision making. Affective decision making involves choices under risky and uncertain conditions

Investigating how brain balances reward and risk and how emotion affects this

How does emotionally centered decision making change with age?

The lateral pre-frontal cortex responsible for self-regulation, matures gradually in adolescents. Teens’ developing brains and high sensitivity to peer pressure might be related to increased tolerance for risky behaviors

Older adults may also make risky decisions as PFC function dimities with age

What does dopamine influence?

Relatively few neurons in the mammalian CNS use dopamine as a NT but these dopaminergic neurons influence brain functions such as voluntary movement and behavioral processes such as mood, reward, addiction, stress, and memory

How does rewards change memory?

When something is very rewarding, the more likely we are to remember it — because dopamine influences the synapses in the entire reward pathway- the hippocampus, amygdala, and the prefrontal cortex- to create emotional associations with rewards.

Mesolimbic pathway

“reward pathway”

major pathway for dopamine, connecting the midbrain’s ventral tegmental area (VTA) to the nucleus accumbens.

Involved in cognitive processing of rewards and motivation. Neurons that release dopamine are activated in response to signals that a reward will be given

What type of reward is most beneficial?

Expectation of a reward that most powerfully influences the emotional reaction.

Reward learning occurs in response to something unexpected- differs from expectation.

Less reward = dopamine down. More reward dopamine up. Same = stable

Why do dopaminergic responses differ?

Some respond more strongly to rewards rather than punishments and vice versa.

Amygdala in various aspects od reward learning and motivation.

“go-getters” who are willing to put in more work have greater dopamine signaling in the striatum and prefrontal cortex, 2 places known to impact motivation and reward.

What causes aggression? 2 things

Aberrant circuitry can lead to inappropriate aggression (symptom of some neuropsychiatric disorders)

Inappropriate activation of the brain’s reward systems in response to violent social stimuli.

Lateral habenula

major node in reward circuitry

encodes punishment by inhibiting dopamine responses. Dysfunction of lateral habenula linked to disorders involving inappropriate aggression.

How is the amygdala linked to negative emotions?

Stimulating some areas can trigger rage and aggression, removing specific sections will make subject more docile