Background and Clinical Significance: Understanding early brain development in infants is essential as identifying an abnormal pattern could accelerate the start of early interventions. There is still limited evidence on how external stimuli (such as tactile, auditory, and visual inputs) influence cortical electrical activity, underscoring the need for integrative studies comparing these modalities in the first months of life. The objective of this paper is to determine the effects of different stimuli (tactile, auditory, and visual) in cortical electrical activity to take advantage of its use in individualized protocols and treatments. Case Presentation: An 8-channel electroencephalography cap was placed on the infant’s head to analyze 10 different conditions depending on the selected stimuli: Kangaroo Care with mother and father, rest, tactile stimuli, visual stimuli, acoustic stimuli, and sleep for 5 min. The environment was the same in all conditions to ensure comparison. All conditions have been able to modify the cortical electrical activity presenting different patterns of electrical activity. Tactile stimuli (massage) showed increased activity in the left parietal region. Acoustic stimuli showed increased activity in the frontal region. Visual stimuli presented different patterns, but with a higher occurrence of artifacts due to baby’s movement. Conclusions: Acoustic stimuli with music increased cortical electrical activity in frontal region, while tactile stimuli increased the left cerebral hemisphere activity. Future studies are needed to support these exploratory results to establish early interventions in pathological conditions.