Subtle but distinct impairments of rats with chemical lesions in the thalamic mediodorsal nucleus, tested in a radial arm maze.

Abstract

The performance of rats trained in a radial arm maze was tested before and after chemical lesions of the thalamic mediodorsal nucleus or the ventral tegmental area. Their behavior was compared with that of a sham-operated con trol group. Lesions were produced with ibotenic acid, a compound that selec tively destroys neurons while apparently leaving fibers of passage intact. Results revealed no intergroup difference in the number of errors performed when all six trials were given in one session without interruption. The group with mediodorsal lesions made, however, significantly more errors than either of the other two groups when a delay of 1 hr was interposed between the first four and the last two trials. Furthermore, these rats differed from rats of the other groups in the number of sessions necessary to reach criterion, in the time needed to finish a session, and in the directness with which a goal was approached. Rats with lesions of the ventral tegmental area did not differ from rats of the sham-operated control group in any of the measures taken. It is suggested that the deficits of rats with mediodorsal lesions resemble qualitatively those found in human patients with lesions of the mediodorsal nucleus.

Thalamic–Cortical–Striatal Circuitry Subserves Working Memory during Delayed Responding on a Radial Arm Maze

“…Rather, these data support the conclusion that the MDNt plays a specific role in the retrieval and use of previously acquired information to guide ongoing behaviors after a delay. As such, the present data are consistent with previous reports that lesions to the rat MDNt do not impair performance of nondelayed radial arm maze tasks (Kessler et al, 1982;Kolb et al, 1982; but see Stokes and Best, 1990) but do disrupt the performance of radial maze tasks with delays between choices (Kessler et al, 1982;Harrison and Mair, 1996;Mair et al, 1998).…”

The neurobiology of thalamic amnesia: Contributions of medial thalamus and prefrontal cortex to delayed conditional discrimination

“…Discrete experimental lesions of MD have been found to produce delay-dependent impairment of decision making in delayed matching to position (DMTP) and DNMTP Young et al, 1996) and other delayed conditional discriminations (Kessler et al, 1982;Zola-Morgan and Squire, 1985), sparing performance at short memory delays. By contrast PFC lesions Porter et al, 2000;Young et al, 1996) produce delay-independent impairment of these tasks, as do lesions of ventral striato-pallidal pathways that connect PFC with medial thalamus ( Fig.…”

Behavioral and frontal cortical metabolic effects of apomorphine and muscimol microinjections into the mediodorsal thalamic nucleus

“…Various behavioral changes have been induced in rodent models by manipulation of the MdT, primarily by utilizing lesion techniques. Behavioral patterns interpreted as spatial memory deficits, memory disruption or attentional dysfunction have been reported (Beracochea etal., 1989;Isseroff etal., 1982;Kessler et al, 1982;Montaron and Buser, 1988;Neave et al, 1993;Stokes and Best, 1988). Complex behaviors such as food hoarding (Mogenson and Wu, 1988) and sleep patterns (Marini etal., 1988) are also clearly influenced by MdT neural disruption.…”

“…The mediodorsal thalamic nucleus (MdT) has been associated with memory (Beracochea etal., 1989;Isseroff et al, 1982;Kessler et al, 1982;Slotnik and Kaneko, 1981;Speedie and Heilman, 1982), attention (Montaron and Buser, 1988;Crowne etal., 1986) and other complex sensory functions (Stokes and Best, 1988). The close association of the MdT with the frontal cortex (FCtx) highlights the MdT's influence on limbic circuits that are important in a variety of human behaviors.…”