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Cone and rod afferent pathways through the mammalian retina. Schematic wiring diagram of the mammalian retina, emphasizing the rod (scotopic) pathways. Left, ON pathways. Right, OFF pathways. Cone circuitry is indicated using just two cone photoreceptors; that in the left half is shown connecting via an ON cone bipolar cell to an ON ganglion cell; that in the right half is shown connecting via an OFF cone bipolar cell to an OFF ganglion cell. The rod pathways are described in the text. From Wässle (276).

Theoretical framework for neuro-immune associative learning. At association time two possible unconditioned stimuli (US) were associated with a conditioned stimulus (CS). The US directly detected by the CNS is defined as a directly perceived US. The one that needs one or more intermediary molecules released by another system in order to be detected by the CNS is called an indirectly perceived US. Any US, directly or indirectly perceived, has two possible afferent pathways to the CNS: a neural afferent pathway and a humoral afferent pathway. At recall time, the CNS can modulate immune functions via these two possible pathways. The humoral efferent pathway may imply changes in neuro-hormones that directly or indirectly modify the immune response. The neural efferent pathway is supported by the direct innervations of primary and secondary lymphoid organs. Features such as novelty, intensity, duration and naturalistic relation to the US may explain the feasibility of associating the CS with the US, along with the stability and strength of such an association. It is also necessary to consider that the immune history (tolerance and memory) of a subject may vary the response to the US, resulting in different associative learning at association time and/or in a different conditioned response at recall time. (Adapted from Pacheco-López, G. et al., in Psychoneuroimmunology, 4th ed., Ader, R., Ed., Academic Press, New York, 2006.)

A, A schematic of the hippocampus illustrates the major afferent pathways to the hippocampus and the position of the stimulation electrode used to activate the perforant path (PP). A. VSD image of a hippocampal slice from a control animal, containing most of each dentate blade and CA3. A snap shot at 25 ms after a burst stimulus applied to the perforant path generates a strong voltage response (red color) in the dentate gyrus that is minimally transmitted as excitation in CA3. B. Calcium imaging of dentate gyrus from control animal and animal 7 days after injection with pilocarpine. PP pathway was stimulated while imaging response from calcium indicator loaded tissues. Images on the left show baseline fluorescence and second images show normalized fluorescence change after electrical stimulation. Traces show normalized fluorescence changes on a randomly selected population of 10 cells from the images. Asterisks (*) indicate cells that responded to the electrical stimulation. Despite strong electrical stimulation majority of dentate granule cells did not have a response in control animal. Middle panels. In the presence of 100 μM picrotoxin in imaging solution, the same electrical stimulation recruited more responsive cells, demonstrating disruption of inhibitory mechanisms. Lower panel. In a slice prepared from an animal 1 week after pilocarpine injection (during the latent period), there was a significant increase in dentate granule cell activation following perforant path stimulation (Image Courtesy of Dr. Cho).

Overview of the major afferent pathways to the hypothalamus. (A) Schematic organization of medial forebrain bundle (MFB). Fibers afferent to the hypothalamus enter the lateral wall of the hypothalamus and are shown in different colors in relation to their anatomical source (amygdala, septal areas, olfactory areas, frontal neocortex). Reciprocal efferent connections from the hypothalamus to the same regions are shown by dotted black lines parallel to the colored lines. Pink fibers (and related reciprocal black dotted lines) indicate the amygdalofugal (and related amygdalopetal) components of the ansa peduncularis, entering the hypothalamus as a part of the medial forebrain bundle. The mammillary body and anterior column of the fornix are colored light blue and lie medial to the course of medial forebrain bundle. (B) Schematic organization of limbic afferents to the hypothalamus via the fornix (fx), stria terminalis (st), stria medullaris (sm), and olfactory tract. Axons enter the rostral portion of the hypothalamus before coursing throughout its entire extent. (C) Course of afferent fibers from the thalamus, subthalamus and zona incerta to the hypothalamus. Efferents from the hypothalamus coursing in the mammillo-subthalamic tract are also shown. On the right side of the image, a three-dimensional reconstruction shows the anatomical structures schematically depicted on the left side.
aap = amygdalofugal and amygdalopetal components of the ansa peduncolaris; ac = anterior commissure; Ah = Ammon horn; al = ansa lenticularis; am = amygdala; ap = ansa peduncularis; ATn = anterior thalamic nucleus; cc = corpus callosum. CN = caudate nucleus; CS = corpus striatum; df = dentate fascia; fl = fasciculus lenticularis; fr = fasciculus retroflexus; ft = fasciculus thalamicus; fx = fornix; H1 = field H1 of Forel; H2 = field H2 of Forel; ha = habenula; hipp = hippocampus; HYP = hypothalamus; ic = internal capsule; iTp-ap = inferior thalamic peduncle of the ansa peduncularis; LTn = lateral thalamic nucleus; mb = mammillary body; MFB = medial forebrain bundle; mst = mammillo-subthalamic tract; MTn = medial thalamic nucleus; mtt = mammillo-thalamic tract; olf-a = olfactory area; olf-n = olfactory nerve; olf =olfactory tubercle; opt = optic tract; pir = piriform cortex; pvs = periventricular system; RF = reticular formation of the brainstem; sa = septal areas; SN = substantia nigra; Sub = subthalamus; zi = zona incerta; III = third ventricle. (From Toni R, Malaguti A, Benfenati F, Martini L: The human hypothalamus: a morphofunctional perspective. J Endocrinol Invest 27 (supp to n.6), 73-94, 2004.)