The progressive deterioration of pattern processing ability in a subject as they progress from mild cognitive impairment (MCI) to severe Alzheimer's disease (AD). In this clock drawing task the subject is asked to draw a clock with the hours and showing the time 2:30. When the person has MCI/early AD the numbers for the hours on the clock are drawn in proper order, but during the time it took to draw the clock the subject forgot that he/she had been asked to show the time 2:30. In the case of the patient with late-stage AD, the drawing bears little resemblance to a clock.
Mattson M
CC BY 3.0
<a rel="nofollow" class="external text" href="https://dx.doi.org/10.3389/fnins.2014.00265">Image file</a> from <cite style="font-style:normal">Mattson M (2014). "<a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4141622">Superior pattern processing is the essence of the evolved human brain</a>". <i>Frontiers in Neuroscience</i>. <a href="https://en.wikipedia.org/wiki/Digital_object_identifier" class="extiw" title="w:Digital object identifier">DOI</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.3389/fnins.2014.00265">10.3389/fnins.2014.00265</a>. <a href="https://en.wikipedia.org/wiki/PMID" class="extiw" title="w:PMID">PMID</a> <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pubmed/25202234">25202234</a>. <a href="https://en.wikipedia.org/wiki/PubMed_Central" class="extiw" title="w:PubMed Central">PMC</a>: <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4141622">4141622</a>.</cite>