updated thal summary w 5b upper vs. lower

Author: rcoreilly

citedrefs.json

@@ -248,7 +248,7 @@ The role of these somatosensory signals in training motor learning in the neocor
 
 The "small loop" in [[#figure_big-loop]] involves different thalamic neurons and areas, specifically ventral-anterior and medial (VA, VM), which are matrix-like and send broad, diffuse connectivity to the most superficial layer of motor cortex. Thus, these areas are not suitable for driving learning (and do not get excitatory driver inputs), but they may play a critical role in driving the transition from a preparatory state of activity to the activity patterns that actually drive motor activity ([[@EconomoViswanathanTasicEtAl18]]; [[@GuoYamawakiSvobodaEtAl18]]; see [[prefrontal cortex|systems-level dynamics]] in the prefrontal cortex page for more discussion).
 
-More abstract state-space analyses of motor activity have consistently shown that preparatory motor activity lives in a _null space_ relative to the activity states that actually drive lower-level motor output pathways ([[@ChurchlandShenoy24]]). These output pathways are driven by layer 5b PT (pyramidal tract) neurons, which are selectively targeted (in their apical tufts) by the matrix-like projections from the VA, VM thalamic areas that receive disinhibitory basal ganglia inputs. Therefore, although it is not as simple as the exclusive activity of these PT neurons by BG inputs, it is likely that the transition from the preparatory null space to the motor output space is facilitated by these BG signals.
+More abstract state-space analyses of motor activity have consistently shown that preparatory motor activity lives in a _null space_ relative to the activity states that actually drive lower-level motor output pathways ([[@ChurchlandShenoy24]]). These output pathways are driven by layer 5b PT (pyramidal tract) neurons (specifically in the lower 5b; [[@EconomoViswanathanTasicEtAl18]]), which are selectively targeted (in their apical tufts) by the broadly-projecting matrix-like pathways from the VA thalamic areas that receive disinhibitory basal ganglia inputs (see [[thalamus#frontal thalamus]]). Therefore, although it is not as simple as the exclusive activity of these PT neurons by BG inputs, it is likely that the transition from the preparatory null space to the motor output space is facilitated by these BG signals.
 
 There are many studies on the nature of motor cortical representations in relation to final motor output parameters. All manner of relevant signals have been decoded from individual neurons, but as usual, the overall [[distributed representations]] are more relevant ([[@GeorgopoulosCarpenter15]]). [[@^AflaloGraziano06a]] showed that final hand posture accounts for most of the variance, consistent with the general nature of muscle synergies as discussed above. However, other factors such as speed, curvature of space, distance and force were also coded.
 

content/media/fig_thalamus_frontal_connectivity.png

@@ -1624,6 +1624,8 @@
 
 <p id="TanFaullCurtis23">Tan, S., Faull, R.L.M., & Curtis, M.A. (2023). The tracts, cytoarchitecture, and neurochemistry of the spinal cord. <i>The Anatomical Record, 306</i>, 777–819. <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/ar.25079">https://onlinelibrary.wiley.com/doi/abs/10.1002/ar.25079</a><a href="http://doi.org/10.1002/ar.25079"> http://doi.org/10.1002/ar.25079</a></p>
 
+<p id="TanibuchiKitanoJinnai09">Tanibuchi, I., Kitano, H., & Jinnai, K. (2009). Substantia nigra output to prefrontal cortex via thalamus in monkeys. I. Electrophysiological identification of thalamic relay neurons. <i>Journal of Neurophysiology, 102</i>, 2933–2945. <a href="http://www.ncbi.nlm.nih.gov/pubmed/19692504">http://www.ncbi.nlm.nih.gov/pubmed/19692504</a></p>
+
 <p id="Taube07">Taube, J.S. (2007). The Head Direction Signal: Origins and Sensory-Motor Integration. <i>Annual Review of Neuroscience, 30</i>, 181–207. <a href="https://www.annualreviews.org/content/journals/10.1146/annurev.neuro.29.051605.112854">https://www.annualreviews.org/content/journals/10.1146/annurev.neuro.29.051605.112854</a><a href="http://doi.org/10.1146/annurev.neuro.29.051605.112854"> http://doi.org/10.1146/annurev.neuro.29.051605.112854</a></p>
 
 <p id="TavernaIlijicSurmeier08">Taverna, S., Ilijic, E., & Surmeier, D.J. (2008). Recurrent collateral connections of striatal medium spiny neurons are disrupted in models of Parkinson's disease. <i>Journal of Neuroscience, 28</i>, 5504–5512. <a href="http://www.jneurosci.org/cgi/content/abstract/28/21/5504">http://www.jneurosci.org/cgi/content/abstract/28/21/5504</a></p>