HYPOTHALAMUS (part of diencephalon) maintains HOMEOSTASIS (temperature, fluid balance, energy balance) by regulating the endocrine system the autonomic system the limbic system Neural AND non-neural (humoral) inputs Neural AND neuro-endocrine outputs

mammillary body anterior commissure infundibulum hypothalamus 3 rd ventricle lateral ventricle 4 th ventricle 3 rd ventricle cerebral aqueduct interventricular foramen

Hypothalamus: medial view and parts mammillary body tuber cinereum median eminence infundibulum

Hypothalamus in horizontal section hippocampus cerebral peduncle substantia nigra inferior colliculus amygdala middle cerebral artery interpeduncular fossa hypothalamus

Hypothalamus in coronal section: anterior Coronal planes BA hypothalamus optic chiasm anterior commissure Sagittal View of Right Hemisphere hypothalamus A. Level of anterior commissure septal nuclei 3 rd ventricle putamen lateral ventricle Basal forebrain

Hypothalamus in coronal section: posterior B: Level of mammillary bodies mammillary body hypothalamus third ventricle thalamus internal capsule lateral ventricle putamen

Hypothalamus: Antero-posterior regions anterior (supraoptic ) posterior (mammillary) middle (tuberal) Preoptic area (not seen here) is antero- lateral to anterior region TC: tuber cincereum ME median eminance INF infundibulum

Hypothalamic nuclei INF=ARC SO: supraoptic nuc SC: suprachasimatic PV: paraventricular INF: infundibular nuc AKA arcuate nuc DMH: dorsomedial hypothalamic nuc VMH: ventromedial hypothalamic nuc PH: posterior hypothalamic nuc AH: anterior hypothalamic nuc MAM: mammilary bodies/nuc

Magnocellular cells: SO and PV. Send axons to posterior pituitary which release oxytocin and ADH into the blood system Oxytocin: parturition/lactation ADH (antidiuretic hormone): conserves water at level of kidneys Parvocelllular cells: (PO, PV, AH, PH, VMH, INF) Small cells involved in control of anterior pituitary. They are found throughout the hypothalamus and especially in the infundibular (arcuate) nucleus.

Hypothalamic Nuclei: Summary of Function Anterior Hypothalamus PO*(preoptic nucleus) water intake, sleep SC circadian rhythms, retina input SO oxytocin, ADH production PV*oxytocin, ADH production AH*temperature (heat loss), sleep- waking * These nuclei also have cells that control the anterior pituitary gland

Hypothalamic Nuclei: Summary of Function Tuberal hypothalamus DMH feeding, rage VMH*feeding, rage INF* (ARC) endocrine control Tuberomamillary nucleus: sleep/waking

Hypothalamic Nuclei: Summary of Function Posterior Hypothalamus MAM memory PH* temperature, (heat conservation), sleep-waking

Regulation of temperature: AH: anterior hypothalamus (heat loss)think A/C “cooling” PH: posterior hypothalamus (heat conservation) Regulation of blood osmolarity: SO: anterior hypothalamus (ADH) PV: anterior hypothalamus (ADH) Regulation of metabolism/emotion: VMH (tubal hypothalamus) feeding/rage TMH (tubal hypothalamus) feeding/rage Regulation of pituitary gland (parvocellular cells): PO, PV, AH, VMH, INF, PH Memory: MeMory = MaM MAM (posterior hypothalamus)

Hypothalamus inputs: overview Hyppocampus–(fornix)  Olfactory and limbicstructures –(MFB)  Amygdala –(stria terminalis)  Retina –(optic tract)  Brainstem (solitary nucleus) –(DLF)  Temperature, osmolarity, hormones –(non-neuronal)   HYPOTHALAMUS

Hypothalamus outputs: overview --(fornix, MFB, VAF)  limbic system --(mammillothalamic tract)  thalamus --(DLF, hypothalamo-spinal tract)  brainstem (autonomic efferents) --(portal system and posterior system)  pituitary  HYPOTHALAMUS

Pituitary gland = hypophysis Anterior pituitary = endocrine cells Posterior pituitary = axon terminals of PV and SO nuclei

infundibulum post. pituitary supraoptic nucleus paraventricular nucleus Hypothalamic axons Posterior pituitary: hypothalamic axons release vasopressin (ADH) and oxytocin to blood

Anterior pituitary gland: endocrine cells releasing hormones median eminence capillaries RFs IFs anterior pituitary sinusoids hypophyseal portal vessels Hormones from endocrine cells releasing & inhibiting factors

Hypothalamus: Head Ganglion for ANS Inputs from –Viscera (afferents via CN X and IX to caudal solitary nucleus) –somatic afferents –limbic system Outputs to –autonomic centers in brainstem – parasympathetic cranial nerve motor nuclei (via DLF) – sympathetic spinal cord motor nuclei (via hypothalamo-spinal tract)

dorsal longitudinal fasciculus hypothalamo -spinal fibers DMNX

hypothalamo -spinal fibers IML= lateral horn

Lesion to descending hypothalamo-spinal fibers (sympathetic pathway) = Horner’s Syndrome Ptosis, miosis and anhydrosis

Limbic System Plays a role in emotions, emotional behaviors, learning, memory and navigation through space Bilateral temperal lobectomy in monkeys: tame, fearless, placid, with a flat affect. Compulsive oral behavior, inappropriate hypersexuality and visual agnosia. Patient HM = bilateral medial temporal lobectomy: demonstrated role of limbic system in learning and memories (hypothalamus important in committing new long term memories)

Emotions Response patterns (emotional expression or behavior) measurable Behavioral: muscle response (e.g. facial expression) ANS activation Hormone secretion Feelings (emotional experience) not easily measurable Negative (anxiety, fear, anger) Positive (euphoria: rarely studied)

Limbic System Anatomically speaking: Limbic lobe Hippocampus (fornix forms the output fibers) Amygdala (stria terminalis forms the output tract) Septal nuclei (Nucleus accumbens)

Limbic lobe: C-shaped medial border of hemisphere septal nuclei subcallosal gyrus cingulate gyrus isthmus of cingulate gyrus parahippocampal gyrus uncus

Septal nuclei H fornixH Basal Forebrain ACH Septal nuclei Play role in autonomic function and emotional behavior Lesion = behavioral changes. Alterations in sexual behavior, rage behavior. Referred to as the “pleasure center” because electrical stimulation is “positively reinforcing”

Nucleus accumbens Implicated in addictive behavior. Recieves dopaminergic input from ventral tegmental area (VTA) Is activated during reward/reinforcer situations VTA N.Acc Reward pathway also includes: MFB, septal nuclei, hypothalamus and frontal cortex

Amygdala (deep to ucus) Sensory input: prefrontal cortex, hippocampus, brainstem Outputs: cortex, hippocampus, hypothalamus, brainstem amygdala

Responsible for learning and maintenance of link between a stimulus and its emotional value. (usually negative emotions) Also influence of smell on appetite Stimulation - fear and anxiety déjà vu Lesion –Kluver-Bucy syndrome Placid, flat affect Fearless Inappropriate social and sexual behavior Hyperoral and overly curious Visual agnosia Memory loss Inability to recognize fear in facial expressions Amygdala

Hippocampus Major input is from the entorhinal cortex and goes to the dentate Major output is back to the entorhinal cortex and to the hypothalamus

dentate gyrus CA3 CA2 CA1 Sub EC EC (entorhinal cortex)—funnels input from all sensory cortices to hippocampus Hippocampus makes a question mark with an arrow head. Question mark is hippocampus formation and arrowhead is dentate gyrus.

Hippocampus function: learning and declarative memory (memory for facts, events, faces, places etc). Memory of place-used for navigation Lesion (patient HM): Unable to lay down (consolidate) new declarative memories Old memories intact No change in intellect No problems with procedural memory

Medial temporal lobe: hippocampus and amygdala amygdala hippocampus

amygdala

Hippocampal circuit (declarative memories) cortex limbic structure hypothalamus thalamus mammillary nuclei hippocampus anterior nucleus cingulate/PHG entorhinal Papez circuit!! mammillo- thalamic tract fornix Anterior limb of internal capsule cingulum

mammillo- thalamic tract fornix

Amygdala circuit cortex limbic structure hypothalamus thalamus amygdala non-mammillary nuclei mediodorsal nucleus prefrontal, temporal olfactory stria terminalis, MFB, and VAF (ventral amygdalofugal) path Anterior limb of internal capsule Uncinate fasciculus and VAF