Mediodorsal but not anterior thalamic nuclei lesions impair acquisition of a conditional discrimination task

Neurobiol Learn Mem. 2015 Nov;125:80-4. doi: 10.1016/j.nlm.2015.07.018. Epub 2015 Aug 5.


The limbic thalamus is a heterogeneous structure with distinctive cortical connectivity. A recent review suggests that the mediodorsal thalamic nucleus (MD), unlike the anterior thalamic nuclei (ATN), may be involved in selecting relevant information in tasks relying on executive functions. We compared the effects of excitotoxic lesions of the MD or the ATN on the acquisition of a simple conditional discrimination in rats. When required to choose from two levers according to auditory or visual cues, ATN rats and sham-lesioned rats performed to the same levels and displayed similar acquisition curves. Under the same conditions, MD rats' acquisition of the task was markedly delayed. This group nevertheless attained nearly normal performances after more extensive training. Furthermore, all rats learned reversal of the original discrimination at the same rate. These results highlight functional specialization within the limbic thalamus and support the notion that MD contributes to the identification of relevant dimensions in conditional tasks during the initial stages of acquisition.

Keywords: Attention; Flexibility; Learning; Limbic thalamus; Rat.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acoustic Stimulation
  • Animals
  • Anterior Thalamic Nuclei / drug effects
  • Anterior Thalamic Nuclei / physiopathology*
  • Conditioning, Operant / drug effects
  • Conditioning, Operant / physiology*
  • Discrimination Learning / drug effects
  • Discrimination Learning / physiology*
  • Male
  • Mediodorsal Thalamic Nucleus / drug effects
  • Mediodorsal Thalamic Nucleus / physiopathology*
  • N-Methylaspartate / toxicity
  • Photic Stimulation
  • Rats
  • Rats, Long-Evans


  • N-Methylaspartate