**3. fNIRS: Beware of methodology!**

The main challenge for researchers is to apply NIRS technology to emotional research as standardized NIRS and fNIRS methods are not yet available.

The first problem is represented by noise, caused by heart-rate variation and Peripheral responses following emotional stimulation. Physical changes often go along with induced state of arousal such as facial muscle contraction or, as said before, increase in heartbeat. The NIRS technique can mitigate this problem by downranging the heartbeat frequency rate (see Section 2.2) although, if not properly set, this can bring to error of data assessment.

Aerobic process and energy consumption associated to muscular contraction may induce significant changes in oxyhemoglobin. However, Schecklmann et al. [2] found no relationship between electromyographic signals and oxyhemoglobin variation during a fluency task. Nevertheless, the influence of peripheric responses was analyzed including limited condition.

rehabilitation process while the entire scientific community agrees on the brain specific individuality that cannot be encoded. We can claim to know each functional brain area, but the information encoded inside is individual and only in a small part conventional. This is the main starting point in order to set individualized rehabilitation models through the use of

Hemoglobin (Hb) - Oxyhemoglobin (HbO) Variation in Rehabilitation Processes Involving…

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In order to allow a cortical reorganization process, there is the need of a specific environmental stimulation, aimed at compensating the impairments. Regardless of which brain area is involved, the aim is to set up a model that can be verified each time with optical imaging techniques. According to this kind of rehabilitation model, the environmental stimulation needs to be grounded on the person's real life experiences so that the choice between different rehabilitation programs is based on the brain activity of a specific area involved during stimulation and verified thanks to NIRS. This choice has to be based not only on customary, logistic and organizational needs but also on cognitive, emotional and motivational patient's

The main goal of the Cerebro rehabilitation model is to improve the functional outcome by supervising rehabilitation choices from time to time and to evaluate the emotional outcome by analyzing Hb-HbO variation in PFC since it is an area involved in emotional control [13].

This neurofunctional rehabilitation model is applied to patients with behavioral cognitive

• Cognitive: like neglect, visuospatial disabilities, aphasia, agnosia, apraxia, amnesia, dyscal-

• Emotional-motivational: like apathy, emotional lability, irritability, depression and anxiety. • Executive (behavioral): like disinhibition, control reduction, discriminatory ability, thought

Each of these impairments involves directly or indirectly the prefrontal cortex since it is

Others that can benefit from this rehabilitation processes are post-stroke patients, cerebrovascular diseases, traumatic brain injuries, multiple sclerosis, encephalitis and post-surgical

Neurodegenerative diseases are excluded from this rehabilitation procedure, apart from multiple sclerosis due to its remittent nature, since there is no evidence yet on how to treat them and due to lack of compliance. However, in case of a motor impairment together with cognitive impairment, that are usually not rehabilitated, our neurofunctional rehabilitation method may be applied in order to monitor brain areas and determine more appropriate choices that

disorder, disorganization, reduced problem solving and lack in self-awareness.

impairment due to brain injury after a complete neuropsychological assessment.

neuronavigation techniques such as fNIRS.

**4.1. Cerebro model's application fields**

Neurofunctional impairments are:

culia and attention deficit.

charged with emotional control.

cancer patients.

needs according to a functional brain activation point of view.

Further signal falsification is given by neural activation to emotional stimulation since variation in Hb-HbO concentration in this case may be due to vasoconstriction. A solution to this is to elicit two different emotional responses and statistically analyze the differences in Hb-HbO concentration between the two responses.

Another problem appears to be the time range (TR) selection that is the time needed for cortical activation to be visually inspected; many studies suggest that oxyhemoglobin drop values indicate cortical activation [3]. Suh et al. [4] claim that cortical direct stimulation induces a rapid increase in deoxyhemoglobin (1–2 s after stimulation) while the total hemoglobin value remains constant. This problem is avoidable by using high temporal resolution in order to evaluate statistically significant changes in Hb-HbO concentration variation.

#### **3.1. Potential fNIRS application**

Theories on PFC's role in emotion processing [5–7] agree on PFC being the key area in which emotional reactions, motivation, attentional processes and behaviors take place.

As PFC is important in emotional processing, the evaluation of emotional intensity with NIRS becomes crucial.

Studies suggest that individual sensitivity to reward and stress may promote depression disorders [8, 9]; these results induce a deeper analysis of eventual biological predisposition that may lead to specific PFC responses to stimuli-induced emotions. Individual differences in terms of emotional responses can help in identifying eventual risk factors.

Using NIRS to analyze PFC activity when stimulated during rehabilitation and the evaluation of the rehabilitation program intensity, considering the abovementioned biological factors, may help to select the optimal rehabilitation method for each patient.

Primary function of emotion is to guide adaptive motor behavior [10]. Few studies focused on this important statement. It is well known that motor activity directly interacts with emotions and mood [11], and it has been shown that there is a bidirectional relationship that has been established between motor function and individual emotional experience [12].
