Neural changes and cognitive changes

Neural changes and cognitive changes

1. Dickstein et al.,(2007) reduction in no of synapses, loss in hippocampus

   • changes in synaptic function, reduction in dendritic length and complexity.
     • leads to slow processing of information, & loss of dendritic cells is the signs of decline in learning & memory performance.
       • neurotransmitter (neurons reduce in length of dendrites, (Dickstein et al 2007)
         • Glutamate (neurotransmitter responsible for excitatory synaptic transmission. Critical for neuronal signalling for learning, memory & other cognitive functions, (Riddle & Schindler, 2007)
   • Synaptic function

2. Attention, working memory and episodic memory declines.

   • Selective attention (Verhaeghen & Cerella, 2002) count no of X in simple and distraction task, older 60-70 yrs take longer than younger to find.
     • Divided attention and switching difficulty, decline in performance of dual task, (Glisky, 2007). Due to reduction of grey & white matter, changes in synaptic function, (Grady, 2012; Dickstein et al., 2007, Riddle & Schindler, 2007).
   • decline in attention due to changes in the PFC and specific regions as grey and white matter essential for information processing.
   • Grady, (2012) indicates that hippocampus and integrity of white matter in corpus collosum reduced in elderly correlated with decline in memory.
   • working memory declines, requires divided attention and the slow information processing is due to reduction of synaptic and dendrites which are essential for neural signalling.
     • change in WM Cabeza, 2002
   • Epsodic memory declines (as storage is dependent on temporal lobe (hippocampus) shrinks Raz et al. 2004 leads to decline in memory tasks.
     • Retrieval depends on storage and encoding which is poor due to reduction of white and grey matter (Allen et al, 2005).
     • older adults might encode new information less meaningfully, not attend to detail and may not be able to interrelate aspects of experience.
       • encoding largely depends on PFC regions
         • storage depends on MTL such as hippocampus
   • Interaction between perception and cognition, sensory and perceptual deficits impact cognitive changes in the brain structure impact cognition.

3. structural changes in the brain impacts neural signalling

   • regional reduction of white and grey matter associated with information processing in brain. Grady, (2012) reduced volume specifically in frontal lobe.
     • Greatest reduction in hippocampus and PFC, correlated with age-related cognitive changes, (Wingfield & Grossman, 2006).
       • (PFC) Allen et al., (2005) examined white and grey matter aging and found greatest change observed in frontal lobe.
         • PFC functional changes (Cabeza, 2002) older adults 60-80 show bilateral recruitment compared to young 20-40 unilateral, bilateral is related to compensatory activation.
           • PFC associated with attention & memory.
   • Medial temporal lobe Raz et al, (2004) MRI measured hippocampus volume, 54 healthy adults age 26-82 yrs, older adults showed annual shrinkage of hippocamps.
     • reduced performance in memory tasks,
       • Pathological changes Alzheimers D, (due to shrinkage of hippocampus, cerebral cotex and enlarged ventricles)
         • AD is progressive neurodegenerative disease.

4. Temporal Lobe associated with Long term Memory

5. Implicit memory and recognition stays stable, while crystallized IQ and emotional reasoning improves.