This research aims to evaluate the effect of cognitive stimulation (CS) on the functioning of the prefrontal cortex (PFC), seeking an analysis of both cerebral hemodynamics in neuroplasticity and aspects related to the initiation of neurodegenerative processes. The intervention presents an individual format and the participants are elderly without or with neurocognitive disorders (NCD). Concretely, to assess the effects of individual CS on global cognition, and mood, as well as to analyze neuronal activity with oxygenation, volume and blood flow in the brain, evaluating the impact of cognitive stimulation on brain hemodynamics. Participants in the intervention group receive two 45 min-session of CS per week for 12 weeks in addition to their treatment as usual. Participants in the control group will maintain their treatment as usual.

Faced with an unprecedented global ageing population and the current COVID-19 pandemic, the risk of social vulnerability increases in the elderly population, promoting the development and aggravation of neurodegenerative diseases, in particular NCD. The diagnostic criteria for this pathology emphasizes cognitive changes, and as such is based clinically on cognitive decline.

The PFC is considered the centre of cognitive function, where it encompasses attention, memory and executive functions.

Attention is the cognitive function that allows us to orient to the relevant stimuli and process them to respond accordingly. Given its functionality, it is distinguished into three types of attention: selective, divided and sustained. Attentional dysfunction can be present in several conditions where cognitive deficit is the main symptom, such as Alzheimer's disease.

With regard to memory, it is subdivided according to time storage, i.e. short or long term. Short-term memory is capable of operating with certain perceived information for a limited space of time and can later be forgotten or transferred to long-term memory. Two other complementary components are distinguished in this type of memory: immediate memory and recent memory. Long-term memory is a latent memory with unlimited capacity that can remain outside the conscious circuit until circumstances require another mode of response. It involves separate, interdependent and dynamic processes of storage, consolidation and evocation. It is made up of two major subsystems: implicit or non-declarative memory, and explicit or declarative memory.

Regarding executive functions, they designate the cognitive processes of control and integration aimed at the execution of behaviour directed at complex objectives, requiring sub-components such as attention, programming, time sequencing, inhibition of competing processes and information, monitoring and selection of strategies. Executive functions include various processes such as working memory, planning, response to reactions and error corrections, cognitive flexibility, inhibition, decision making.

There is evidence that in the early stages of NCD, people are able to learn and improve their cognitive function through interventions such as CS. CS is recommended by the National Institute for Health and Clinical Excellence as a non-pharmacological therapy for people with mild to moderate NCD and is an intervention where the cognitive domains are not used in isolation but integrated. An individual format is associated with better results. In a systematic review on CS, studies have shown strong evidence that CS has a positive impact on cognitive function, depression, daily life activities and behaviour for people with NCD.

However, no studies are known that have analyzed prefrontal cortex activity in the elderly population associated with a functional method of infrared spectroscopy (fNIRS). This method provides information on hemodynamic changes associated with cortical activation by measuring in a non-invasive way changes in the relative ratios of deoxygenated hemoglobin (HHb) and oxygenated hemoglobin (HbO2).

Monitoring and recording the dynamics in the PFC of the elderly during a cognitive stimulation programme with the fNIRS method may contribute to expanding knowledge about aspects related to neurodegenerative processes and cognitive function in the elderly.

Inclusion Criteria:

• Being 65 years of age or older.
• Being able to communicate and understand.
• Being a native Portuguese speaker.
• Educational level equal to or higher than 4 years old.
• Have given informed consent for the project, duly completed and signed, after prior information.
• Have a score of 22 or more points in the MMSE.

Exclusion Criteria:

• Suffering from an acute or severe illness that prevent participation in the intervention sessions.
• Severe sensory and physical limitations that prevent participation.
• Low level of consciousness and minimal attention span.
• Presence of severe neuropsychiatric symptoms (such as agitation, psychosis, severe depressive and anxiety symptoms, apathy), or presence of uncontrolled delirium that would prevent participation in the sessions.
• History of seizures or cerebrovascular disease.
• Movement disorders diagnosis.
• Psychoactive substances consumption.