In animal models, lesion studies have confirmed the mediodorsal thalamus
Thalamus
The thalamus is a large mass of gray matter in the dorsal part of the diencephalon of the brain with several functions such as relaying of sensory signals, including motor signals to the cerebral cortex, and the regulation of consciousness, sleep, and alertness.
The medial dorsal nucleus (or dorsomedial nucleus of thalamus) is a large nucleus in the thalamus. It is believed to play a role in memory.
Does the mediodorsal thalamus play a role in memory and cognition?
Aug 09, 2013 · In animal models, lesion studies have confirmed the mediodorsal thalamus (MD) has a role in memory and other cognitive tasks, although the extent of deficits is mixed. Anatomical tracing studies confirm at least three different subgroupings of the MD: medial, central, and lateral, each differentially interconnected to the prefrontal cortex (PFC).
What is mediodorsal thalamus damage?
Dense amnesia can result from damage to the medial diencephalon in humans and in animals. In humans this damage is diffuse and can include the mediodorsal nuclei of the thalamus. In animal models, lesion studies have confirmed the mediodorsal thalamus (MD) has a role in memory and other cognitive tasks, although the extent of deficits is mixed. Anatomical tracing studies …
What is the largest part of the medial thalamus?
In animal models, lesion studies have confirmed the mediodorsal thalamus (MD) has a role in memory and other cognitive tasks, although the extent of deficits is mixed. Anatomical tracing studies confirm at least three different subgroupings of the MD: medial, central and lateral, each differentially interconnected to the prefrontal cortex.
What are the effects of mediodorsal thalamic lesions in rats?
It has been suggested that lesions to the MD could dis- EXPERIMENTAL MEDIODORSAL THALAMUS LESIONS rupt pathways leading to the PFC and may affect processes that Earlier work in animals focused on determining the one criti- are typically governed by the PFC, including attention, inhibi- cal structure within the medial thalamus that was causing the tion, …
Where does Mediodorsal nucleus of thalamus project?
It relays inputs from the amygdala and olfactory cortex and projects to the prefrontal cortex and the limbic system and in turn relays them to the prefrontal association cortex.
What is the role of the thalamus in movement?
Motor thalamus (Mthal) is implicated in the control of movement because it is strategically located between motor areas of the cerebral cortex and motor-related subcortical structures, such as the cerebellum and basal ganglia (BG).Nov 11, 2013
What is ventral thalamus?
Definition. The ventral thalamus, as usually defined in the adult brain, consists of the reticular nucleus, the zona incerta, and the ventral lateral geniculate nucleus (Fig. 15.1). To this, many authors add the nucleus of the fields of Fore!'
What are the cerebellum's functions?
The cerebellum (which is Latin for “little brain”) is a major structure of the hindbrain that is located near the brainstem. This part of the brain is responsible for coordinating voluntary movements. It is also responsible for a number of functions including motor skills such as balance, coordination, and posture.Jun 16, 2020
What is the basic function of the thalamus quizlet?
Functions: The thalamus receives sensory information from other areas of the nervous system and sends this information to the cerebral cortex. The thalamus is also important for processing information related to movement.
What is the function of ventral lateral nucleus?
The ventral lateral nucleus of the thalamus (VL) serves as a central integrative center for motor control, receiving inputs from the cerebellum, striatum, and cortex and projecting to the primary motor cortex.
What is the function of ventral posterior nucleus?
The ventral posterior nucleus receives neuronal input from the medial lemniscus, spinothalamic tracts, and trigeminothalamic tract. It projects to the somatosensory cortex and the ascending reticuloactivation system.
What does the thalamus do simple explanation?
The thalamus relays sensory impulses from receptors in various parts of the body to the cerebral cortex. A sensory impulse travels from the body surface towards the thalamus, which receives it as a sensation. This sensation is then passed onto the cerebral cortex for interpretation as touch, pain or temperature.Feb 27, 2019
What is the role of the medial thalamus in memory?
However, understanding how the medial thalamus contributes to memory and other cognitive functions has been much overlooked in cognitive neuroscience and neuropsychology. This mainly stems from the theoretical notion held over the past 50 years that the medial temporal lobes act exclusively as the brain's long-term declarative memory center. Despite this prevailing account, human patients can also suffer dense amnesia following damage in the medial diencephalon (diencephalic amnesia, thalamic amnesia). Brain damage that causes memory loss and other cognitive deficits in this region occurs after traumatic head injury, stroke, hemorrhage, thiamine deficiency, or chronic alcoholism (Korsakoff's syndrome). However, this brain damage is not circumscribed in clinical patients as many of the structures of the medial diencephalon (medial thalamus, mammillary bodies, and mammillothalamic tract) suffer combined damage due to their small size, close proximity to one another and fibers of passage coursing through the region. The medial thalamic structures most frequently identified as being critical for the memory deficits are anterior (AT), mediodorsal (MD), and the intralaminar (IL)/midline thalamic nuclei. The mammillary bodies and white matter fiber tracts, particularly the internal medullary lamina and the mammillothalamic tract, are also strongly implicated in human amnesic cases and animal models. Thus, the neural basis of the memory deficits associated with the medial diencephalon continues to be debated in the literature ( Harding et al., 2000; Kopelman, 2002; Van der Werf et al., 2003a; Cipolotti et al., 2008; Aggleton et al., 2011; Carlesimo et al., 2011; Pergola et al., 2012; Vann, 2013 ).
What is the MD in the brain?
For the purposes of this review, the structure will be referred to as the mediodorsal thalamus (MD) and at some points will be distinguished by some of its subdivisions, that is, the magnocellular mediodorsal thalamus (MDmc) or medial MD, the parvocellular mediodorsal thalamus (MDpc) or central MD, and a lateral grouping that will include the densocellular (MDdc) and pars multiforms (MDmf) mediodorsal thalamic nuclei or lateral MD (MDl).
How do rats use T-mazes?
In rats, many studies assess the rats' ability to forage for food using T-mazes, water mazes and radial arm mazes, taking advantage of their natural curiosity to explore novel environments for food. Many strategies can be used by the animals to complete these tasks successfully ( Dudchenko, 2001 ). One strategy involves spatial navigation based on the use of extra maze cues (e.g., door, windows, lights, posters, experimenter, etc.) within the testing environment (spatial cues) to help guide their optimal exploration and ensure they do not return to the same location twice. Animals with selective neurotoxic lesions to the MD show comparable performance to control animals when they use spatial cues to guide their navigation in radial arm maze tasks ( Beracochea et al., 1989; Hunt and Aggleton, 1998a; Mitchell and Dalrymple-Alford, 2005 ), unless they incorporate a delay ( Harrison and Mair, 1996; Floresco et al., 1999) or produce more widespread damage that also includes the AT ( Stokes and Best, 1988, 1990a, b; Hunt and Aggleton, 1991, 1998a ). It has been proposed that MD deficits in delay tasks are presumably a consequence of widespread disruption to PFC functioning ( Hunt and Aggleton, 1998b ). Floresco et al. (1999) contrasted working memory performance using a spatial delayed responding task and non-delayed spatial tasks to show that the interaction between the PFC and the MD mediates “context-dependent retrieval and manipulation of recently acquired information.” Furthermore, this study provided evidence, via lidocaine infusions into the MD, to show that MD alone is not sufficient to affect episodic-like memory processing on spatial memory tasks ( Floresco et al., 1999 ). Instead, it is widely accepted that spatial memory processing deficits related to the medial thalamus are governed by the anterior thalamic nuclei and their interconnections to the extended hippocampal system, also known as the Delay-Bryon neural circuit ( Aggleton and Brown, 1999 ).
What causes dense amnesia?
Dense amnesia can result from damage to the medial diencephalon in humans and in animals. In humans this damage is diffuse and can include the mediodorsal nuclei of the thalamus. In animal models, lesion studies have confirmed the mediodorsal thalamus (MD) has a role in memory and other cognitive tasks, although the extent of deficits is mixed.
Introduction
Anatomy of The MD
- Many of the structures in the brain can go by several names and this is the case with the MD, which is also referred to as medial dorsal thalamic nuclei, nucleus medialis dorsalis, and the dorsomedial thalamus. For the purposes of this review, the structure will be referred to as the mediodorsal thalamus (MD) and at some points will be distinguished by some of its subdivision…
Animal Lesion Studies
- Studying memory and cognition with animal models is extremely insightful, in addition to being a useful way to overcome some of the limitations that are inherent in the clinical evidence. There are many advantages to developing animal models of memory processing. Surgical lesions in animals can normally be somewhat more circumscribed and involve subtotal, complete or even …
Electrophysiology
- A recent review of single unit recordings in macaques (Watanabe and Funahashi, 2012) provides insight into how the MD contributes to successful performance during working memory (delayed oculomotor response) tasks. The review highlights clear interplay between the MD and PFC, as suggested by other studies. For example, neurons in the MD have shown cue-, delay- and respon…
Theories About MD Involvement in Memory Processing
- Aggleton and Brown (1999) suggested that the MD, and the perirhinal cortex of the medial temporal lobe, may play a role in a system responsible for familiarity-based recognition processes. However, this proposal remains debated because the direct neural connections between the MD and perirhinal cortex are sparse and clinical evidence (Pergola et al., 2012) and …
Re-Evaluating Mediodorsal Thalamus in Memory and Where to from Here
- As indicated from the above survey of the contribution of the MD to specific forms of memory and decision-making, some conclusions have been drawn but much debate remains. Nevertheless, the evidence thus far provides some understanding and certainly helps with future directions. Thus, the animal evidence (and also the clinical evidence although not reviewed here) simply doesn't s…
Conflict of Interest Statement
- The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.