Neuroscience Chapter on Memory and Senses

A neurological circuit proposed by James Papez in 1937, originally believed to control emotions; It includes the hypothalamus (mammillary bodies), anterior nucleus of the thalamus, cingulate cortex, and hippocampus.

The removal of the medial temporal lobes, including the hippocampus, in Patient H.M. resulted in severe anterograde amnesia (inability to form new memories) and partial retrograde amnesia (loss of memories from before the surgery).

Explicit memory, also known as declarative memory, is the conscious recollection of facts and events. It can be further divided into semantic memory (general knowledge) and episodic memory (personal experiences).

Implicit memory, also called procedural memory, is the unconscious learning of skills and habits. It is demonstrated through performance rather than conscious recall.

The hippocampus plays a crucial role in forming new long-term memories and consolidating short-term memories into lasting ones.

The limbic system, expanded upon by Paul MacLean, encompasses the limbic lobe (including the cingulate cortex, parahippocampal gyrus, amygdala, hippocampus, and hypothalamus). It integrates emotion, behavior, and memory.

The five traditional senses are: smell (olfaction), sight (vision), hearing (audioception), taste (gustation), and touch (tactioception).

Other senses beyond the traditional five include temperature (thermoception), kinesthetic sense (proprioception), pain (nociception), balance (equilibrioception), and various internal stimuli detected by chemoreceptors.

These are bipolar neurons located in the olfactory epithelium of the nasal cavity. They possess cilia that contain odorant receptors, which are responsible for detecting specific smells. The binding of odorants to these receptors triggers action potentials, initiating the olfactory signal.

These are synaptic sites within the olfactory bulb where axons from olfactory receptor neurons (ORNs) connect with mitral and tufted cells.

These cells receive signals from ORNs in the glomeruli and relay them to higher brain areas, including the olfactory cortex and limbic system.

These are inhibitory interneurons that modulate signal transmission in the olfactory bulb, helping to refine odor processing by reducing background noise.

These are inhibitory interneurons that also play a role in modulating signal transmission, but they act between mitral and tufted cells to further refine the olfactory signal.

These are chemical messengers that are used by inhibitory cells in the olfactory bulb to regulate olfactory signal processing. Examples include GABA, dopamine, and glycine.

ORNs with the same receptor type project their axons to the same glomerulus. This creates a map for odor processing, where different scents are represented by distinct glomeruli.

Axons from ORNs converge onto a single glomerulus in the olfactory bulb. This convergence allows for the processing of complex odor mixtures and the identification of subtle differences in smells.

The process of how the brain translates the activation of different olfactory receptors into specific smells. Each smell activates a unique combination of glomeruli, creating a distinct pattern that is interpreted by the brain.

The primary olfactory cortex (POC) in the uncus serves as the starting point. It connects to various brain regions like the entorhinal cortex, olfactory tubercle, thalamus, and orbitofrontal cortex, linking smell perception to other functions.

The ability to detect and identify different smells. Humans can distinguish thousands of odours.

The lowest concentration of a substance that can be detected by sensory receptors. For smell, this threshold can be incredibly low, indicating our nose's high sensitivity.

In humans, smell mainly plays an aesthetic role, influencing experiences like taste, memory, and emotional responses. But it is not as crucial for survival as it is for many animals.

Animals often rely heavily on smell for survival. It helps them find food, locate mates, and avoid dangers.

This part processes sensory information and emotional learning related to smells. It learns the connection between odors and emotions.

This section links smells to emotions, creating emotional responses to specific odors.

The part of the amygdala that receives input from the olfactory bulb and olfactory cortex and is involved in processing olfactory information.

This part of the amygdala receives highly processed information from various sensory areas of the cortex and affects how sensory information is processed. It also plays a role in modulating cortical activity through connections with the thalamus and striatum.

Region of the amygdala that receives input from the hippocampus, insula, orbitofrontal cortex, and other parts of the amygdala. It projects to the hypothalamus and brainstem, influencing autonomic, endocrine, and motor responses related to emotions, eating, drinking, and sexual behavior.

A fiber bundle connecting the hippocampus to the hypothalamus, playing a role in memory formation and retrieval.

The hippocampus's tri-synaptic circuit, consisting of three important synapses, is involved in memory formation, consolidation, and retrieval, especially for spatial and episodic memories.

The first stage of the hippocampal tri-synaptic circuit, where the entorhinal cortex activates granule cells in the dentate gyrus, enabling the differentiation between similar experiences.

The second stage of the hippocampal tri-synaptic circuit, where granule cells in the dentate gyrus send axons to CA3 pyramidal cells, aiding in recalling memories from partial cues.

The third stage of the hippocampal tri-synaptic circuit, where CA3 pyramidal cells transmit information to CA1 for final processing and output to other brain regions, contributing to memory storage and retrieval.

The hypothalamus is the brain region that acts as a control center for many vital bodily functions.

The hypothalamus regulates essential processes like breathing, heart rate, body temperature, and digestion, ensuring everything runs smoothly.

The HPA axis (Hypothalamic-Pituitary-Adrenal axis) is the body's primary stress response system. When you're stressed, the hypothalamus triggers the release of stress hormones.

The mammillary nucleus is a brain structure within the hypothalamus that plays a critical role in memory formation.

The hypothalamus receives information from various parts of the body, including sensory, visual, and olfactory signals.

The hypothalamus receives signals from the frontal lobe of the brain, allowing it to integrate high-level cognitive information.

The hippocampus, involved in memory, sends signals to the mammillary nucleus within the hypothalamus, connecting memory and hypothalamus function.

The hypothalamus integrates various signals from the nervous and hormonal systems to maintain homeostasis and adaptive responses.

This tract carries signals between the amygdala and hypothalamus, influencing emotional and autonomic responses.

Fibers from the dorsomedial and midline nuclei of the thalamus communicate with the hypothalamus, facilitating reciprocal interaction.

These fibers link the midbrain tegmentum with the hypothalamus, contributing to autonomic function and arousal.

These fibers descend through the reticular formation, controlling the autonomic nervous system. They influence sympathetic and parasympathetic outflow.

This tract connects the mammillary body to the anterior thalamic nucleus, linking memory and emotional processing.

This tract originates in the mammillary body and projects to the reticular formation, influencing autonomic and arousal functions.

The hypothalamus regulates melatonin production through its control of the suprachiasmatic nucleus (SCN).

This area within the hypothalamus regulates temperature. Lesions can result in hyperthermia (inability to dissipate heat) or hypothermia (impaired ability to generate heat).