Spatial-Frequency–Dependent Changes in Cortical Activation before and after Patching in Amblyopic Children

2004 ◽  
Vol 45 (10) ◽  
pp. 3531 ◽  
Author(s):  
Avery H. Weiss ◽  
John P. Kelly
Keyword(s):  
Spatial Frequency ◽  
Cortical Activation ◽  
Frequency Dependent ◽  
Before And After

Dynamic Changes in the Cortex-Basal Ganglia Network After Dopamine Depletion in the Rat

2008 ◽  
Vol 100 (1) ◽  
pp. 385-396 ◽  
Author(s):  
Cyril Dejean ◽  
Christian E. Gross ◽  
Bernard Bioulac ◽  
Thomas Boraud
Keyword(s):  
Basal Ganglia ◽  
Local Field ◽  
Signal Transmission ◽  
Local Field Potentials ◽  
Cellular Level ◽  
Cortical Activation ◽  
Field Potentials ◽  
Dopamine Depletion ◽  
Indirect Pathway ◽  
Before And After

It is well established that parkinsonian syndrome is associated with alterations in the temporal pattern of neuronal activity and local field potentials in the basal ganglia (BG). An increase in synchronized oscillations has been observed in different BG nuclei in parkinsonian patients and animal models of this disease. However, the mechanisms underlying this phenomenon remain unclear. This study investigates the functional connectivity in the cortex-BG network of a rodent model of Parkinson's disease. Single neurons and local field potentials were simultaneously recorded in the motor cortex, the striatum, and the substantia nigra pars reticulata (SNr) of freely moving rats, and high-voltage spindles (HVSs) were used to compare signal transmission before and after dopaminergic depletion. It is shown that dopaminergic lesion results in a significant enhancement of oscillatory synchronization in the BG: the coherence between pairs of structures increased significantly and the percentage of oscillatory auto- and cross-correlograms. HVS episodes were also more numerous and longer. These changes were associated with a shortening of the latency of SNr response to cortical activation, from 40.5 ± 4.8 to 10.2 ± 1.07 ms. This result suggests that, in normal conditions, SNr neurons are likely to be driven by late inputs from the indirect pathway; however, after the lesion, their shorter latency also indicates an overactivation of the hyperdirect pathway. This study confirms that neuronal signal transmission is altered in the BG after dopamine depletion but also provides qualitative evidence for these changes at the cellular level.

scholarly journals Changes in cortical activation during mirror reading before and after training: an fMRI study of procedural learning

2001 ◽  
Vol 10 (3) ◽  
pp. 207-217 ◽  
Author(s):  
Jan Kassubek ◽  
Klaus Schmidtke ◽  
Hubert Kimmig ◽  
Carl H. Lücking ◽  
Mark W. Greenlee
Keyword(s):  
Procedural Learning ◽  
Cortical Activation ◽  
Fmri Study ◽  
Before And After ◽  
Mirror Reading

Targeted Loss of Proteoglycans Results in Changes of Frequency-Dependent Viscoelastic Behavior of the Intact Articular Cartilage

2012 ◽  
Author(s):  
Simon Y. Tang ◽  
Tamara Alliston
Keyword(s):  
Articular Cartilage ◽  
Mechanical Behavior ◽  
Viscoelastic Behavior ◽  
Enzymatic Digestion ◽  
Cartilage Tissue ◽  
Indentation Modulus ◽  
Frequency Dependent ◽  
Bovine Articular Cartilage ◽  
Before And After ◽  
Tan Δ

Cartilage is a multi-phasic, viscoelastic material that derives its mechanical behavior of its primary constituents including collagen, proteoglycans, and water. The complex mechanical function of cartilage depends critically on the composition and balance of these constituents. We sought to determine the effects of proteoglycan loss on both the time- and frequency-dependent mechanical behavior of articular cartilage. Using cathepsin d, an enzyme that specifically cleaves proteoglycans, we assessed the in situ mechanical behavior of intact bovine articular cartilage before and after enzymatic digestion using microindentation over loading frequencies ranging between 0.5 hz to 20 hz. The loss of proteoglycans does not affect the elastic components of mechanical behavior (indentation modulus; p = 0.67), but have significant consequences on the viscoelastic components (tan δ; p<0.001). Moreover, the changes in the viscoelastic mechanical behavior are more pronounced at higher loading frequencies (p<0.001). Taken together, these results suggest that proteoglycans are critical for providing dynamic stability for the cartilage tissue.

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