In mid-stage Alzheimer’s disease, sensory processing undergoes noticeable changes that affect how individuals perceive and respond to their environment. This stage is marked by a decline in the brain’s ability to handle sensory information efficiently, which can impact attention, reaction to stimuli, and overall cognitive function.
One key change is in the brain’s arousal system, which helps regulate alertness and focus. Normally, when something important happens—like a sudden sound or visual cue—the brain responds by increasing arousal, helping a person pay attention and react quickly. In mid-stage Alzheimer’s, this arousal response becomes slower and weaker. For example, pupil dilation, a sign of arousal when noticing something new, is reduced and delayed. This means patients may not notice or respond to important sensory cues as effectively as before. This diminished arousal is linked to slower and more variable reaction times, making it harder to engage with the environment promptly.
Another aspect is the slowing of brain activity rhythms, especially in the alpha frequency range, which is important for processing sensory input and maintaining attention. This slowing disrupts the normal coordination between brain arousal and sensory processing, further impairing the ability to filter and respond to sensory information. As a result, patients may experience difficulties in focusing on relevant stimuli while ignoring distractions.
Additionally, changes in brain connectivity, particularly in areas responsible for integrating sensory information and coordinating movement, contribute to altered sensory experiences. The prefrontal cortex, which plays a role in planning and decision-making, becomes less effective in managing sensory integration. This can lead to challenges in interpreting complex sensory environments, such as busy or noisy places, and may affect motor responses like walking or reaching.
Overall, sensory processing in mid-stage Alzheimer’s is characterized by a reduced ability to detect, interpret, and react to sensory signals. This decline is tied to changes in brain arousal mechanisms, slowed neural rhythms, and impaired connectivity in sensory and cognitive networks. These changes contribute to the difficulties patients face in daily activities that require attention to sensory cues and quick, coordinated responses.
