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Sensory Processing, Cognitive Inhibition, and Brain Health

For some people, cognitive abilities may decline with age. One of the most frequent changes is a decrease in inhibitory signals in the cortex, which leads to increased cortical chatter, or noise. This increased brain activity is meaningless, not evolutionarily or behaviorally useful, and detracts from the ability to do common tasks. This “noise in the brain” may signal the onset of worsening sensory processing as well as cognitive decline. However, it is not inevitable. Many patients do not show this increased brain noisiness, and they also tend to retain their cognitive abilities. What makes the difference?

For some older adults, reduced auditory processing abilities as well as decreased speed of auditory processing are a problem.1 Visual processing can also be slower, and suppression of non-task information may be less effective.2 This is likely due to an interaction of deficits, both in inhibition and processing speed.2 The integration of information from multiple senses, like auditory and visual information, may also be impaired.3

Yet neuroplasticity is bidirectional, so age doesn’t have to lead to declines in cognitive abilities. Environmental and lifestyle factors play a major role in determining whether brain function declines, is maintained, or even improves with age or otherwise. For example, patients who are consistently exposed to loud volumes of noise (like in some processing plants, or in tunnels with traffic) display similar auditory processing deficits as many of those older individuals.4 In animal models, repeated exposure to high volumes of noise causes brain changes that reverse some of the indicators of maturation.5 Restoring the animals to a normal acoustic environment reverses those changes, bringing the brain back to a more mature state.5 This suggests that with appropriate interventions, many processing deficits can be reversed. Reducing the noise in the brain and training the brain to focus on relevant stimuli is doable.

Indeed, brain exercises and training have been shown to reverse task-specific deficits in older adults,6,7 including for visual tasks8 and speech processing.9 Training and practice may increase the brain’s ability to inhibit brain activity that does not contribute to task success, reducing the noise.10

IFM has two resources to learn more about this exciting topic. The 2017 Annual Conference Proceedings include a number of neuroscientists and clinical speakers who dove into these topics, including:

References

  1. Harris KC, Wilson S, Eckert MA, Dubno JR. Human evoked cortical activity to silent gaps in noise: effects of age, attention, and cortical processing speed. Ear Hear. 2012;33(3):330-339. doi:10.1097/AUD.0b013e31823fb585.
  2. Gazzaley A, Clapp W, Kelley J, McEvoy K, Knight RT, D’Esposito M. Age-related top-down suppression deficit in the early stages of cortical visual memory processing. Proc Natl Acad Sci U S A. 2008;105(35):13122-13126. doi:10.1073/pnas.0806074105.
  3. Stothart G, Kazanina N. Auditory perception in the aging brain: the role of inhibition and facilitation in early processing. Neurobiol Aging. 2016;47:23-34. doi:10.1016/j.neurobiolaging.2016.06.022.
  4. Kujala T, Shtyrov Y, Winkler I, et al. Long-term exposure to noise impairs cortical sound processing and attention control. 2004;41(6):875-881. doi:10.1111/j.1469-8986.2004.00244.x.
  5. Zhou X, Panizzutti R, de Villers-Sidani E, Madeira C, Merzenich MM. Natural restoration of critical period plasticity in the juvenile and adult primary auditory cortex. J Neurosci. 2011;31(15):5625-5634. doi:10.1523/JNEUROSCI.6470-10.2011.
  6. Ball K, Berch DB, Helmers KF, et al. Effects of cognitive training interventions with older adults: a randomized controlled trial. JAMA. 2002;288(18):2271-2281.
  7. Smith GE, Housen P, Yaffe K, et al. A cognitive training program based on principles of brain plasticity: results from the Improvement in Memory with Plasticity-based Adaptive Cognitive Training (IMPACT) study. J Am Geriatr Soc. 2009;57(4):594-603. doi:10.1111/j.1532-5415.2008.02167.x.
  8. Mishra J, Rolle C, Gazzaley A. Neural plasticity underlying visual perceptual learning in aging. Brain Res. 2015;1612:140-151. doi:10.1016/j.brainres.2014.09.009.
  9. Anderson S, White-Schwoch T, Choi HJ, Kraus N. Training changes processing of speech cues in older adults with hearing loss. Front Syst Neurosci. 2013;7:97. doi:3389/fnsys.2013.00097.
  10. Oldrati V, Patricelli J, Colombo B, Antonietti A. The role of dorsolateral prefrontal cortex in inhibition mechanism: a study on cognitive reflection test and similar tasks through neuromodulation. 2016;91:499-508. doi:10.1016/j.neuropsychologia.2016.09.010.

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