**4. Frequency following response: evaluation in children and adolescents**

Auditory impairment is almost invariably associated with language and communication deficits. Learning a spoken language depends on assimilating the acoustic and phonetic elements of a language [32]. The development of the central auditory nervous system begins in intrauterine life and continues until adolescence, over which time hearing abilities become more complex and elaborate.

Because of the close relationship between hearing, language, and learning, it is extremely important to monitor hearing over the course of life. Especially in children, be it pre-school or school age, the aim should be to monitor auditory function, either through behavioral or electrophysiological assessments. The ideal would be a combination of both behavioral and electrophysiological methods, so that with numerous evaluations there are crosschecks which allow a more accurate diagnosis to be made.

The electrophysiological procedure traditionally used in clinical practice is the click ABR. However, in evaluating children with language deficits, this type of sound stimulus is not ideal for making diagnoses. Assessments using verbal sound stimuli, such as used in FFR, appear to be more effective and reliable in cases of learning problems or school difficulties [6]. Evaluation via an FFR allows a detailed analysis of how verbal stimuli are encoded in the central auditory nervous system to be done.

The FFR allows fine-grained auditory processing deficits associated with realworld communication skills to be identified. As well as being used for the early identification of auditory processing, it can also be used to assess hearing across different clinical populations [33, 34]. This electrophysiological procedure can provide reliable and objective information about acoustic patterns such as timing, pitch, and timbre [35]. These three elements can be evaluated using different parts of the FFR, as follows:


Simplistically, it can be said that the FFR helps in understanding which speech sounds were spoken (their timing and harmonic cues) and who said it (pitch cues) [36]. In addition, an FFR test can be performed under two conditions: (i) in silence (presentation of verbal stimuli only), and (ii) in noise (presentation of verbal stimuli plus background noise).

In children and adolescents, studies have shown that FFRs change in latency as age increases. FFRs of children aged around 5 years appear to be very similar to the responses of children aged 8–12. However, the FFR pattern of children under 5 years has a somewhat different morphology and latency. According to Johnson et al. [33], the differences in children younger than 3 years are more evident in the initial portion of the responses (the onset), while in older children the change is more evident in the final portion (the offset) [3, 37].

Initial studies have focused on understanding the FFRs in children and adolescents under silent conditions and in subjects who have normal hearing and typical development. For the benefit of clinical audiologists, some of these studies are summarized below (**Tables 4–9**).

**Table 10** shows the parameters used in children and adolescents at the Electrophysiology Department of the State University of Campinas using Biologic equipment and BioMARK software.

Because FFR is a new procedure, unstudied pathologies are gradually being added and, little by little, we are gaining new information about what effects the pathologies have on the responses of affected children and adolescents.

The FFRs of children diagnosed as poor readers frequently present as alterations in the timing and magnitude of timbre components [38]. The perception of the duration of a sound stimulus is essential for proficient reading, and the FFR can evaluate or monitor a decline in temporal and spectral precision. Children and adolescents with dyslexia commonly have difficulty perceiving speech sounds either in silence or in competing noise backgrounds. If a child has difficulty in perceiving speech sounds, their reading can be severely impaired [39]. Recently, Sanfins et al. [6] highlighted the importance of FFR as a biological marker in scholastic difficulties.

FFR evaluation in children who have suffered from secretory otitis media in the first 6 years of life, and who have undergone myringotomy for bilateral ventilation tube placement, exhibit changes in their FFR compared to normal children [5]. This study found that evaluating the FFR seems to be a promising method of identifying


*Cz: vertex, M1: left mastoid, M2: right mastoid, ms: millisecond, dB: decibel, SPL: sound pressure level, s: second, Hz: hertz.*

**145**

*The Frequency Following Response: Evaluations in Different Age Groups*

changes in the coding of speech stimuli in these children which might be undetected using traditional electrophysiological evaluation. The changes in their electrophysiological responses might serve as an alert to parents and educators, who can then adopt strategies to minimize the negative consequences on language development

Another possibility for using FFR assessment may be in monitoring an auditory training program or even tracking the effect of therapeutic interventions. Studies have shown that children with learning disabilities can benefit from an auditory remediation program, and it might therefore be usefully accompanied by FFR examinations (because FFRs have good repeatability in test and retest) [40, 41]. In addition, bilingual children can also be monitored through FFR assessment. Researchers have confirmed that neural perception of speech seems to be more consistent in bilinguals than in monolinguals [42, 43]. Bilingual experience during childhood may favor plasticity in the neuronal coding of sound and improve

Recently, the neurophysiological aspects of speech perception have been investigated in cases of autism spectrum disorder (ASD). The results showed that children with ASD tend to have changes in the sensation of pitch (frequency), which might explain a withdrawal from speech reception. The fundamental frequency (F0) and its harmonics contain speech information which is essential in conveying affect [44], so changes in FFRs are consistent with a defect in perceiving prosody. The inference is that prosody deficits in some ASD patients may derive from an inability

Traditionally, FFR testing is done by presenting verbal stimuli through an insert earphone with a silent background. However, the perception of speech in a noisy background is a much discussed topic. In the presence of noise, normally hearing individuals need to make constant adjustments in their central auditory nervous system to satisfactorily understand and process speech information. Of course, there are others who, in the presence of competing noise, experience great difficulty

The evaluation of FFR in the presence of noise can be effectively used to diagnose children with learning disabilities [47]. Thus, identification of such children could lead to improvements in their reading and writing skills and in daily

**5. Frequency following response: evaluation in adults and the elderly**

In the adult and elderly population, the need for detailed audiological investigation increases when the patient complains of hearing difficulties, even if auditory

The evaluation of the FFR first involves time and prosody recordings, which provide important information about consonant and vowel discrimination and also aid in the perception of intonation [48]. For adults, but especially in the elderly, participation in these sorts of tests can assist in rehabilitation, either using a hearing

The clinical usefulness of the FFR in gauging how well auditory information is being processed is unquestionable. In adults and the elderly, many studies have already been done to identify how the FFR can help in diagnosing complaints related to central auditory processing, thereby allowing better rehabilitation. The latencies (mean and standard deviation) for adults and the elderly are presented in **Table 11**. The values come from Skoe et al. [19] who used Biologic and

to encode and transmit auditory information in the brainstem [45].

*DOI: http://dx.doi.org/10.5772/intechopen.85076*

fundamental frequency perception (F0).

in understanding speech [46].

thresholds appear normal.

aid or auditory training (or both).

communication.

and academic achievement.

#### **Table 10.**

*Parameters of FFR in children and adolescents.*

#### *The Frequency Following Response: Evaluations in Different Age Groups DOI: http://dx.doi.org/10.5772/intechopen.85076*

*The Human Auditory System - Basic Features and Updates on Audiological Diagnosis and Therapy*

Initial studies have focused on understanding the FFRs in children and adolescents under silent conditions and in subjects who have normal hearing and typical development. For the benefit of clinical audiologists, some of these studies are

**Table 10** shows the parameters used in children and adolescents at the Electrophysiology Department of the State University of Campinas using Biologic

pathologies have on the responses of affected children and adolescents.

**Parameter Settings**

Software BioMARK Electrode montage Cz, M1, and M2 Stimulated ear Right ear Stimulus Speech Stimulus type Syllable /da/ Stimulus duration 40 ms Stimulus polarity Alternating Stimulus intensity 80 dB SPL Stimulus rate 10.9/s Number of sweeps 6000

Equipment Biologic Navigator Pro

Replicability Twice for 3000 sweeps

*Cz: vertex, M1: left mastoid, M2: right mastoid, ms: millisecond, dB: decibel, SPL: sound pressure level, s: second, Hz:* 

Assessment condition Watching a movie

Transducer Insert

Impedance 1k Ohms Window 85.33 ms 85.33 ms Filter 100–2000 Hz Artifact rejection >10%

*Parameters of FFR in children and adolescents.*

Because FFR is a new procedure, unstudied pathologies are gradually being added and, little by little, we are gaining new information about what effects the

The FFRs of children diagnosed as poor readers frequently present as alterations in the timing and magnitude of timbre components [38]. The perception of the duration of a sound stimulus is essential for proficient reading, and the FFR can evaluate or monitor a decline in temporal and spectral precision. Children and adolescents with dyslexia commonly have difficulty perceiving speech sounds either in silence or in competing noise backgrounds. If a child has difficulty in perceiving speech sounds, their reading can be severely impaired [39]. Recently, Sanfins et al. [6] highlighted the importance of FFR as a biological marker in

FFR evaluation in children who have suffered from secretory otitis media in the first 6 years of life, and who have undergone myringotomy for bilateral ventilation tube placement, exhibit changes in their FFR compared to normal children [5]. This study found that evaluating the FFR seems to be a promising method of identifying

summarized below (**Tables 4–9**).

equipment and BioMARK software.

scholastic difficulties.

**144**

*hertz.*

**Table 10.**

changes in the coding of speech stimuli in these children which might be undetected using traditional electrophysiological evaluation. The changes in their electrophysiological responses might serve as an alert to parents and educators, who can then adopt strategies to minimize the negative consequences on language development and academic achievement.

Another possibility for using FFR assessment may be in monitoring an auditory training program or even tracking the effect of therapeutic interventions. Studies have shown that children with learning disabilities can benefit from an auditory remediation program, and it might therefore be usefully accompanied by FFR examinations (because FFRs have good repeatability in test and retest) [40, 41]. In addition, bilingual children can also be monitored through FFR assessment. Researchers have confirmed that neural perception of speech seems to be more consistent in bilinguals than in monolinguals [42, 43]. Bilingual experience during childhood may favor plasticity in the neuronal coding of sound and improve fundamental frequency perception (F0).

Recently, the neurophysiological aspects of speech perception have been investigated in cases of autism spectrum disorder (ASD). The results showed that children with ASD tend to have changes in the sensation of pitch (frequency), which might explain a withdrawal from speech reception. The fundamental frequency (F0) and its harmonics contain speech information which is essential in conveying affect [44], so changes in FFRs are consistent with a defect in perceiving prosody. The inference is that prosody deficits in some ASD patients may derive from an inability to encode and transmit auditory information in the brainstem [45].

Traditionally, FFR testing is done by presenting verbal stimuli through an insert earphone with a silent background. However, the perception of speech in a noisy background is a much discussed topic. In the presence of noise, normally hearing individuals need to make constant adjustments in their central auditory nervous system to satisfactorily understand and process speech information. Of course, there are others who, in the presence of competing noise, experience great difficulty in understanding speech [46].

The evaluation of FFR in the presence of noise can be effectively used to diagnose children with learning disabilities [47]. Thus, identification of such children could lead to improvements in their reading and writing skills and in daily communication.
