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The only sensory information that is not relayed by the thalamus into the cerebral cortex is information related to smell (olfaction).
The thalamus (from the Greek thalamos or inner chamber) transmits 98 percent of sensory information to the cortex, including vision, taste, touch and balance; the only sense that doesn’t pass through this brain region is smell.
When light hits the retina of the eye, that information makes a stopover in the thalamus before being sent to the visual cortex of the brain to be processed. Similarly, auditory and somatosensory (touch) information is routed through the thalamus before traveling to cortex for more complex processing.
The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are routed through the thalamus before being directed to other areas of the brain for processing (Figure 1).
Midbrain and Hindbrain Structures. The midbrain is comprised of structures located deep within the brain, between the forebrain and the hindbrain. The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located in the midbrain (Figure).
The basal forebrain, near the front and bottom of the brain, also promotes sleep and wakefulness, while part of the midbrain acts as an arousal system.
The thalamus is extremely important to the regulation of the human nervous system. It is the center of information processing, and is what maintains consciousness, organizes subconscious information and regulates the very survival of the human being.
Thalamus is a part of the diencephalon. It is located deep in the forebrain, present just above the midbrain. One thalamus is present on each side of the third ventricle.
The thalamus has multiple functions, generally believed to act as a relay station, or hub, relaying information between different subcortical areas and the cerebral cortex. The thalamus plays a major role in regulating arousal, the level of awareness, and activity. Damage to the thalamus can lead to permanent coma.
Following a thalamic stroke, full recovery can take anywhere from a week or two to several months. Depending on how severe the stroke was and how quickly it was treated, you may have some permanent symptoms.
Researchers report the thalamus plays a far more active role in visual processing in the context of learning than previously thought. Source: Max Planck Institute. The cerebral cortex is where we learn and think, form impressions of our environment, control conscious behaviour, and store memories.
According to the textbooks, the upstream regions of the brain like the thalamus only contribute to these processes by forwarding information from the sensory organs to the corresponding regions of the cerebral cortex and filtering the information, if necessary. …
“But all three groups found that the thalamus, a subcortical system, plays an important role in working memory — it’s not just a receiver of the signal, it’s an essential partner with the cortex.” The new papers are also notable in that they study working memory in rodents rather than primates.
For over half a century, learning and memory have been intimately associated with the hippocampal formation, often leaving the functional contribution of other brain regions overlooked. However, the thalamus also has a long-standing link to memory.
While the thalamus is classically known for its roles as a sensory relay in visual, auditory, somatosensory, and gustatory systems, it also has significant roles in motor activity, emotion, memory, arousal, and other sensorimotor association functions.
Thalamic Connections Mnemonic
For example, visual information from your retina travels to the lateral geniculate nucleus of the thalamus, which is specialized to handle visual information, before being sent on to the primary visual cortex (the main area for visual processing in the brain).
The thalamic nuclei relay and modulate information incoming from the periphery to the cerebral cortex. Basically, almost all ascending neural pathways first synapse within a thalamic nucleus, where the information is sorted, integrated, and analysed by the thalami before they are sent further to the cerebral cortex.
The LGN is considered a first-order thalamic nucleus on the basis of its close relationship with the retina. In contrast, the pulvinar nucleus—another thalamic nucleus involved in vision—is considered a second-order nucleus, as it primarily receives afferent input from the cortex.
There are two major structures lying inferiorly to the thalamus. Anteroinferiorly is the hypothalamus, caudal to the hypothalamic sulcus. Directly inferior to the thalamus is the cerebral peduncle and the cerebral aqueduct of Sylvius.
The thalamus is a small structure within the brain located just above the brain stem between the cerebral cortex and the midbrain and has extensive nerve connections to both. The primary function of the thalamus is to relay motor and sensory signals to the cerebral cortex.
The thalamus is located deep within the brain in the cerebral cortex, adjacent to the hypothalamus. It is a symmetrical structure, situated on top of the brain stem and on either side of the third cortex.
Visual information from the outside world is conveyed from the retinal receptors through the sensory relay nucleus of the thalamus, the lateral geniculate nucleus (LGN), to primary visual cortex (V1 or striate cortex).